Scholars@Duke
Kenneth C. Hall

Kenneth C. Hall

Julian Francis Abele Distinguished Professor
Thomas Lord Department of Mechanical Engineering and Materials Science
kenneth.c.hall@duke.edu
184 Hudson Eng Ctr, Box 90300, Durham, NC 27708-0300
184 Hudson Eng Ctr, Box 90300, Durham, NC 27708

Selected Publications

Identification of the Aeromechanical Parameters of a Compressor Rotor from Blade Tip Timing Data

Conference Journal of Turbomachinery · July 1, 2024 This article presents a maximum likelihood approach to identifying the mistuning, aerodynamic forcing functions, and aerodynamic influence coefficients of compressor rotor blades from noisy experimental measurements of blade deflection. The maximum likelih ... Full text Cite

A Fluid-Structure Interaction Tool Using a Van der Pol-Based Reduced-Order Model for Buffet and Nonsynchronous Vibrations

Journal Article Journal of Turbomachinery · January 1, 2023 This paper builds upon a two-degree-of-freedom Van der Pol oscillator-based reducedorder model for studying the mechanisms around nonsynchronous vibrations (NSV) in turbomachinery. One degree tracks the fluid motion utilizing a combination of a traditional ... Full text Cite

Extending a Van Der Pol-Based Reduced-Order Model for Fluid-Structure Interaction Applied to Non-Synchronous Vibrations in Turbomachinery

Journal Article Journal of Turbomachinery · March 1, 2022 This paper expands upon a multi-degree-of-freedom, Van der Pol oscillator used to model buffet and nonsynchronous vibrations (NSV) in turbines. Two degrees-of-freedom are used, a fluid tracking variable incorporating a Van der Pol oscillator and a classic ... Full text Cite

Modeling of Fluid-Structure Interaction

Chapter · January 1, 2022 Modeling of aerodynamic forces has now moved beyond the classical potential flow theory at least in the research community and to some degree in engineering practice. These more sophisticated fluid models are based upon the Euler or Navier- Stokes equation ... Full text Cite

Modern Analysis for Complex and Nonlinear Unsteady Flows in Turbomachinery

Chapter · January 1, 2022 The field of turbomachinery is undergoing major advances in aeroelasticity and this chapter provides an overview of these new developments in the key enabling methodology of unsteady aerodynamic modeling. Also see the earlier discussions in chapters “Aeroe ... Full text Cite

Unsteady Pressure Analysis of an Oscillating Cylinder Exhibiting Non-Synchronous Vibrations

Conference AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022 · January 1, 2022 When an unsteady aerodynamic instability interacts with the natural modes of vibration of a rigid body, lies a phenomenon known as Non-Synchronous Vibrations (NSV), often referred to as Vortex-Induced Vibrations (VIV). These vibrations cause blade failure ... Full text Cite

Unsteady Pressures Analysis of an Oscillating Airfoil Exhibiting Nonsynchronous Vibrations as Applied to Turbomachinery

Conference AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022 · January 1, 2022 When an unsteady aerodynamic instability interacts with the natural modes of vibration of a rigid body, lies a phenomenon known as Non-Synchronous Vibrations (NSV), also known as Vortex-Induced Vibrations (VIV). These vibrations cause blade failure in jet ... Full text Cite

Blade Vibration and Its Effect on the Optimal Performance of Helicopter Rotors

Journal Article Journal of Aircraft · January 1, 2022 In this paper, we develop a computationally efficient frequency-domain model that can be used to compute the required shaft power and vibratory loads for a trimmed helicopter rotor with flexible blades in forward flight. The aerodynamic forces and power ar ... Full text Cite

AN IMPROVED PRELIMINARY DESIGN TOOL FOR TURBOMACHINERY BLADES USING VAN DER POL BASED REDUCED-ORDER MODEL FOR NON-SYNCHRONOUS VIBRATIONS

Conference Proceedings of the ASME Turbo Expo · January 1, 2022 Starting from an oscillating cylinder, this paper navigates the shift of a Van der Pol based Reduced-Order Model from that simple case to airfoil and turbomachinery blade. The structure will be free to vibrate under the influence of a von Karman vortex str ... Full text Cite

A FLUID-STRUCTURE INTERACTION TOOL USING A VAN DER POL BASED REDUCED-ORDER MODEL FOR BUFFET AND NON-SYNCHRONOUS VIBRATIONS

Conference Proceedings of the ASME Turbo Expo · January 1, 2022 This paper builds upon a two-degree-of-freedom Van der Pol oscillator based Reduced-Order Model for studying the mechanisms around Non-Synchronous Vibrations (NSV) in turbomachinery. One degree tracks the fluid motion utilizing a combination of a tradition ... Full text Cite

Extending a van der pol based reduced-order model for fluid-structure interaction applied to non-synchronous vibrations in turbomachinery

Conference Proceedings of the ASME Turbo Expo · January 1, 2021 This paper expands upon a multi-degree-of-freedom, Van der Pol oscillator used to model buffet and Nonsynchronous Vibrations (NSV) in turbines. Two degreesof-freedom are used, a fluid tracking variable incorporating a Van der Pol oscillator and a classic s ... Full text Cite

ISUAAAT15 Special Issue

Journal Article Journal of Turbomachinery · October 1, 2019 Full text Cite

Special issue on the 17th ISROMAC conference

Journal Article Journal of Turbomachinery · February 1, 2019 Full text Cite

Minimum loss load, twist, and chord distributions for coaxial helicopters in hover

Conference Journal of the American Helicopter Society · January 1, 2017 This paper presents an approach for determining the optimal (minimum power) geometry of a hovering coaxial rotor using blade element momentum theory, including swirl. The analysis accounts for the presence of a finite number of blades using the Prandtl tip ... Full text Cite

Axisymmetric potential flow model of single or coaxial actuator disks

Conference Annual Forum Proceedings - AHS International · January 1, 2016 This papcr prcscnts a computationally cfficicnt method for computing the axisymmetric three-dimensional flow field induced by the trailing vortex system of either a single actuator disk or a pair of closely spaced coaxial actuator disks. A rotor in axial f ... Cite

Comparison of Numerical Methods for the Prediction of Time-Averaged Flow Quantities in a Cooled Multistage Turbine

Conference ASME Turbo Expo 2015: Turbine Technical Conference and Exposition · June 15, 2015 An unsteady simulation of a two-stage, cooled, high pressure turbine cascade is achieved by applying the harmonic balance method, a mixed time domain and frequency domain computational fluid dynamic technique for efficiently solving periodic unsteady flows ... Cite

A variational approach to multipoint aerodynamic optimization of conventional and coaxial helicopter rotors

Conference Annual Forum Proceedings - AHS International · May 2015 © 2015 by the American Helicopter Society International, Inc. We present a variational approach to the multipoint aerodynamic design optimization of conventional and coaxial helicopter rotors. The optimal design problem is cast as a variational statement t ... Cite

Optimum design of compound helicopters that use higher harmonic control

Journal Article Journal of Aircraft · January 1, 2015 The optimal design of a compound helicopter comprised of counterrotating coaxial rotors, a propeller, and optionally a fixed wing is investigated. The blade geometry, azimuthal blade pitch inputs, optimal shaft angle (rotor angle of attack), and division o ... Full text Cite

Minimum loss load, twist and chord distributions for coaxial helicopters in Hover

Conference Annual Forum Proceedings - AHS International · January 1, 2015 We present an approach for determining the optimal (minimum power) torque-balanced coaxial hovering rotor using Blade Element Momentum Theory including swirl. We quantify the effects of the swirl component of induced velocity on performance, optimal induce ... Cite

Optimum design of compound helicopters using higher harmonic control

Conference Annual Forum Proceedings - AHS International · January 1, 2014 We investigate the optimal design of a compound helicopter comprised of counter-rotating coaxial rotors, a propeller, and optionally a fixed wing. We determine the blade geometry, azimuthal blade pitch inputs, optimal shaft angle (rotor angle of attack), a ... Cite

Minimum power requirements and optimal rotor design for conventional and compound helicopters using higher harmonic control

Conference Annual Forum Proceedings - AHS International · September 9, 2013 We present a method for computing the optimal aerodynamic performance of conventional and compound helicopters in trimmed forward flight with a limited set of design variables and control inputs, including conventional and higher harmonic blade control, an ... Cite

Discrete adjoint method for nonlinear aeroelastic sensitivities for compressible and viscous flows

Conference 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference · August 2, 2013 Presented is a discrete adjoint approach for computing nonlinear aeroelastic design sensitivities for transonic and viscous flows based on Reynolds Averaged Navier-Stokes computational fluid dynamic models. The method is based on a harmonic balance nonline ... Full text Cite

Compact implementation strategy for a harmonic balance method within implicit flow solvers

Journal Article AIAA Journal · June 1, 2013 A two-step approximate factorization technique for implementing a computationally stable nonlinear unsteady frequency-domain harmonic balance solution method within existing implicit computational fluid dynamic flow solver codes is presented. The approach ... Full text Cite

Stabilization of explicit flow solvers using a proper-orthogonal- decomposition technique

Conference AIAA Journal · May 1, 2013 A new numerical technique for the stabilization of explicit computational-fluid-dynamic solvers is presented. When using computational-fluid-dynamic codes to solve practical problems one sometimes finds the solution fails to converge due to the presence of ... Full text Cite

Harmonic balance methods applied to computational fluid dynamics problems

Journal Article International Journal of Computational Fluid Dynamics · February 1, 2013 In this paper, we briefly review the classical harmonic balance method, and describe the adaptation of the method required for its application to computational fluid dynamics models of unsteady time periodic flows. We describe several variations of the met ... Full text Cite

Unsteady simulation of a two-stage cooled high pressure turbine using an efficient non-linear harmonic balance method

Conference Proceedings of the ASME Turbo Expo · January 1, 2013 The harmonic balance method is a mixed time domain and frequency domain approach for efficiently solving periodic unsteady flows. The implementation described in this paper is designed to efficiently handle the multiple frequencies that arise within a mult ... Full text Cite

A van der pol based reduced-order model for non-synchronous vibration (NSV) in turbomachinery

Conference Proceedings of the ASME Turbo Expo · January 1, 2013 This paper demonstrates the potential of using a multidegree- of-freedom, traditional van der Pol oscillator to model non-synchronous vibration (NSV) in turbomachinery. It is shown that the two main characteristics of NSV are captured by the reduced-order, ... Full text Cite

Effect of rider position on bicycle stability

Conference ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) · January 1, 2013 Bicycle stability has been of interest to dynamicists and athletes since before J. W. Whipple described the canonical model for bicycle motion in 1899. Since then, the subject has fascinated many who sought to find a simple way to describe the essence of s ... Full text Cite

The effect of aerodynamic asymmetries on turbomachinery flutter

Journal Article Journal of Fluids and Structures · January 1, 2013 In this paper, the effect of aerodynamic asymmetries on the flutter characteristics of turbomachinery blades is investigated. Specifically, the present method is used to study the effect of leading edge blending in loaded and unloaded rotors. The unsteady ... Full text Cite

An automatic differentiation based nonlinear reduced order modeling technique for unsteady separated flows

Conference 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition · December 1, 2012 This paper discusses the development and implementation of an automatic differentiation based nonlinear reduced order model for unsteady separated flows. The objective of the research presented herein has been to test the capability and limits of the metho ... Full text Cite

Stabilization of explicit flow solvers using a proper orthogonal decomposition technique

Conference 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition · December 1, 2012 A new numerical technique for the stabilization of explicit computational fluid dynamic (CFD) solvers is presented. When using CFD codes to solve practical problems, one sometimes finds the solution fails to converge due to the presence of a small number o ... Full text Cite

Developing a reduced-order model to understand nonsynchronous vibration (NSV) in turbomachinery

Conference Proceedings of the ASME Turbo Expo · January 1, 2012 This paper demonstrates the potential of using a multidegree- of-freedom, traditional van der Pol oscillator to model Non-Synchronous Vibration (NSV) in turbomachinery. It is shown that the two main characteristics of NSV are captured by the reduced-order, ... Full text Cite

Unsteady simulation of a 1.5 stage turbine using an implicitly coupled nonlinear harmonic balance method

Conference Proceedings of the ASME Turbo Expo · January 1, 2012 The harmonic balance method implemented within STARCCM+ is a mixed frequency/time domain computational fluid dynamic technique, which enables the efficient calculation of timeperiodic flows. The unsteady solution is stored at a small number of fixed time l ... Full text Cite

Simulation of unsteady turbomachinery flows using an implicitly coupled nonlinear harmonic balance method

Conference Proceedings of the ASME Turbo Expo · December 1, 2011 A nonlinear harmonic balance method for the simulation of turbomachinery flows is presented. The method is based on representing an unsteady, time periodic flow by a Fourier series in time and then solving a set of mathematically steady-state equations to ... Full text Cite

Harmonic balance analysis of limit cycle oscillations in turbomachinery

Journal Article AIAA Journal · July 1, 2011 A harmonic balance technique for the analysis of limit cycle oscillations of turbomachinery blades is presented. This method couples a computational fluid dynamics model to a single-degree-of-freedom structural dynamic model of the turbomachinery blades. T ... Full text Cite

F-16 fighter aeroelastic computations using a harmonic balance implementation of the OVERFLOW 2 flow solver

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · December 16, 2010 Presented are flutter-onset trends of the F-16 fighter computed using a harmonic balance version of the NASA OVERFLOW 2 flow solver code. The harmonic technique enables one to model unsteady aerodynamics and aeroelastic response in the frequency domain wit ... Cite

Harmonic balance analysis of limit cycle oscillations in turbomachinery

Conference 46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit · December 1, 2010 A harmonic balance technique for the analysis of limit cycle oscillations (LCO) of turbomachinery blades is presented. This method couples a computational fluid dynamics (CFD) model to a single-degree of freedom structural dynamic model of the turbomachine ... Cite

A variational method for computing the optimal aerodynamic performance of conventional and compound helicopters

Journal Article Annual Forum Proceedings - AHS International · December 1, 2010 Abstract We present a variational method for computing the optimal aerodynamic performance of conventional and compound helicopters in trimmed flight. The optimal circulation distribution minimizes the sum of the induced and viscous power required to devel ... Cite

A variational method for computing the optimal aerodynamic performance of conventional and compound helicopters

Conference Annual Forum Proceedings - AHS International · November 15, 2010 We present a variational method for computing the optimal aerodynamic performance of conventional and compound helicopters in trimmed flight. The optimal circulation distribution minimizes the sum of the induced and viscous power required to develop a pres ... Cite

A variational method for computing the optimal aerodynamic performance of conventional and compound helicopters

Journal Article Journal of the American Helicopter Society · October 1, 2010 We present a variational method for computing the optimal aerodynamic performance of conventional and compound helicopters in trimmed flight. The optimal circulation distribution minimizes the sum of the induced and viscous power required to develop a pres ... Full text Cite

Using automatic differentiation to create a nonlinear reduced-order-model aerodynamic solver

Journal Article AIAA Journal · January 1, 2010 A novel nonlinear reduced-order-modeling technique for computational aerodynamics and aeroelasticity is presented. The method is based on a Taylor series expansion of a frequency-domain harmonic balance computational fluid dynamic solver residual. The firs ... Full text Cite

Harmonic balance analysis of blade row interactions in a transonic compressor

Journal Article Journal of Propulsion and Power · January 1, 2010 In this paper we apply the harmonic balance technique to analyze an inlet guide vane and rotor interaction problem, and compare the computed flow solutions to existing experimental data. The computed results, which compare well with the experimental data, ... Full text Cite

Forced response analysis of aerodynamically asymmetric cascades

Conference 46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit · January 1, 2010 The effect of aerodynamic asymmetries on forced response characteristics of cascades is investigated. Specifically, the present method is used to study the effect of leading edge blending in loaded rotors. The unsteady aerodynamic response of the blades to ... Full text Cite

A variational method for computing the optimal aerodynamic performance of conventional and compound helicopters

Conference Annual Forum Proceedings - AHS International · 2010 Abstract We present a variational method for computing the optimal aerodynamic performance of conventional and compound helicopters in trimmed flight. The optimal circulation distribution minimizes the sum of the induced and viscous power required to devel ... Cite

The Effects of aerodynamic asymmetric perturbations on forced response of bladed disks

Journal Article Journal of Turbomachinery · October 1, 2009 Most of the existing mistuning research assumes that the aerodynamic forces on each of the blades are identical except for an interblade phase angle shift. In reality, blades also undergo asymmetric steady and unsteady aerodynamic forces due to manufacturi ... Full text Cite

Improved flutter boundary prediction for an isolated two-degree-of-freedom airfoil

Journal Article Journal of Aircraft · January 1, 2009 A novel method of computing the flutter boundary for an isolated airfoil based on a high-fidelity computational fluid dynamics model reveals unusual behavior in a critical transonic range. Inviscid and viscous predictions of the flutter boundary for the tw ... Full text Cite

Theoretical predictions of F-16 fighter limit cycle oscillations for flight flutter testing

Journal Article Journal of Aircraft · January 1, 2009 A computational investigation of the flutter onset and limit cycle oscillation behavior of various F-16 fighter weapons and stores configurations is presented. A nonlinear harmonic balance compressible Reynolds-averaged Navier-Stokes computational fluid dy ... Full text Cite

Unsteady flow computation using a harmonic balance approach implemented about the OVERFLOW 2 flow solver

Conference 19th AIAA Computational Fluid Dynamics Conference · January 1, 2009 A novel approach for implementing a nonlinear unsteady frequency domain harmonic balance solution technique about existing implicit computational fluid dynamic flow solvers is presented. This approach uses an explicit discretization of the harmonic balance ... Full text Cite

Application of enforced motion to study 2-D cascade lock-in effect

Conference 47th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition · January 1, 2009 The vortex lock-in effect has been well-studied for an oscillating cylinder and numerous experimental and computational data are available. However, only recently has this phenomenon been observed for two-dimensional isolated airfoils as well as turbine ca ... Full text Cite

Harmonic balance analysis of forced response in a transonic compressor

Conference 47th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition · January 1, 2009 A harmonic balance technique for the analysis of nonlinear forced response phenomenon in a two-row transonic compressor is presented. Using the present approach, each blade row is modeled using a computational grid spanning a single blade passage regardles ... Full text Cite

The effect of aerodynamic asymmetries on turbomachinery flutter

Conference 47th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition · January 1, 2009 In this paper, the effect of aerodynamic asymmetries on the flutter characteristics of turbomachinery blades is investigated. Specifically, the present method is used to study the effect of leading edge blending in loaded and unloaded rotors. The unsteady ... Full text Cite

Efficient design method for non-synchronous vibrations using enforced motion

Conference Proceedings of the ASME Turbo Expo · December 1, 2008 This paper presents the results of a new enforced motion method using harmonic balance computational fluid dynamics (CFD) analysis to design for NSV. Currently, most researchers employ a time domain CFD technique to directly find the frequency of the under ... Full text Cite

The effects of aerodynamic asymmetric perturbations on forced response of bladed disks

Conference Proceedings of the ASME Turbo Expo · December 1, 2008 Most of the existing mistuning research assumes that the aerodynamic forces on each of the blades are identical except for an interblade phase angle shift. In reality, blades also undergo asymmetric steady and unsteady aerodynamic forces due to manufacturi ... Full text Cite

Aerodynamic asymmetry analysis of unsteady flows in turbomachinery

Conference Proceedings of the ASME Turbo Expo · December 1, 2008 A nonlinear harmonic balance technique for the analysis of aerodynamic asymmetry of unsteady flows in turboma-chinery is presented. The present method uses a mixed time-domain/frequency-domain approach that allows one to compute the unsteady aerodynamic re ... Full text Cite

Reduced order models in unsteady aerodynamic models, aeroelasticity and molecular dynamics

Conference ICAS Secretariat - 26th Congress of International Council of the Aeronautical Sciences 2008, ICAS 2008 · December 1, 2008 The state of reduced order modeling of unsteady aerodynamic flows for the efficient calculation of fluid-structure interaction (aeroelasticity) is discussed as well as very recent work on olecular dynamics simulations. Starting with either a time domain or ... Cite

Computationally fast harmonic balance methods for unsteady aerodynamic predictions of helicopter rotors

Conference Journal of Computational Physics · June 1, 2008 A harmonic balance technique for the analysis of unsteady flows about helicopter rotors in forward flight and hover is presented in this paper. The aerodynamics of forward flight are highly nonlinear, with transonic flow on the advancing blade, subsonic fl ... Full text Cite

Aerodynamic Asymmetry Analysis of Unsteady Flows in Turbomachinery

Journal Article Journal of Turbomachinery · 2008 Cite

A new solution method for unsteady flows around oscillating bluff bodies

Journal Article Solid Mechanics and its Applications · January 1, 2008 Full text Cite

Virtual aeroelastic flight testing for the F-16 fighter with stores

Conference Collection of Technical Papers - U.S. Air Force T and E Days, 2007(Test and Evaluation · November 5, 2007 In the following, we present computational aeroelastic flutter onset and limit cycle oscillation response trends for various stores and weapons configurations of the F-16 fighter. A nonlinear harmonic balance compressible Reynolds averaged Navier-Stokes co ... Cite

Nonlinear analysis of unsteady flows in multistage turbomachines using harmonic balance

Journal Article AIAA Journal · May 1, 2007 A harmonic balance technique for the analysis of two-dimensional linear (small-disturbance) and nonlinear unsteady flows in multistage turbomachines is presented. The present method uses a mixed time-domain/frequency-domain approach that allows one to comp ... Full text Cite

A novel harmonic balance analysis for the Van Der Pol oscillator

Journal Article International Journal Of Non-linear Mechanics · January 2007 This study focuses on a novel harmonic balance formulation, the high-dimensional harmonic balance method. To investigate a non-linearity in the damping term, the system chosen for study is the Van der Pol's oscillator. Both unforced and forced oscillators ... Cite

The effect of unsteady aerodynamic asymmetric perturbations on flutter

Conference Proceedings of the ASME Turbo Expo · January 1, 2007 Nearly all turbomachinery aeroelastic analyses assume that the blades are "tuned" aerodynamically. That is, all blades experience identical steady and unsteady loads (except for an interblade phase shift). This paper presents the results of a perturbations ... Full text Cite

Three-dimensional unsteady multi-stage turbomachinery simulations using the harmonic balance technique

Conference Collection of Technical Papers - 45th AIAA Aerospace Sciences Meeting · January 1, 2007 In this paper, we propose an extension of the Harmonic Balance method for three-dimensional, unsteady, multi-stage turbomachinery problems modeled by the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. This time-domain algorithm simulates the t ... Full text Cite

An investigation of the sensitivity of F-16 fighter flutter onset and limit cycle oscillations to uncertainties

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · December 1, 2006 A computational investigation of flutter onset and limit cycle oscillations of the F-16 fighter using a nonlinear frequency-domain harmonic-balance approach is presented. In this latest study, we examine the sensitivity of computed aeroelastic behavior to ... Cite

Message from the conference chair

Conference Proceedings of the ASME Turbo Expo · November 14, 2006 Cite

Probabilistic flutter analysis of a mistuned bladed disk

Conference Proceedings of the ASME Turbo Expo · 2006 This paper presents the results of a probabilistic flutter study of a mistuned bladed disk using a high fidelity model including both structural and aerodynamic coupling. The approach used in this paper is relatively fast because it does not require any ad ... Cite

A comparison of classical and high dimensional harmonic balance approaches for a Duffing oscillator

Journal Article J. Comput. Phys. (USA) · 2006 The present study focuses on a novel harmonic balance formulation, which is much easier to implement than the standard/classical harmonic balance method for complex nonlinear mathematical models and algorithms. Both harmonic balance approaches are applied ... Full text Link to item Cite

Static/dynamic correction approach for reduced-order modeling of unsteady aerodynamics

Journal Article Journal of Aircraft · 2006 Presented is a newly devised static/dynamic correction approach for eigenvector expansion based reduced-order modeling (ROM). When compared to the fundamental Ritz ROM formulation, along with the static and multiple static correction ROM approaches, the te ... Cite

Modeling cylinder flow vortex shedding with enforced motion using a harmonic balance approach

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 2006 In recent years, new aeromechanical problems have been encountered in turbomachinery. In particular, non-synchronous vibrations (NSV) in blades have been observed by engine companies and occur as a result of flow instabilities. As a first step towards bett ... Full text Cite

Using automatic differentiation to create a nonlinear reduced order model of a computational fluid dynamic solver

Conference Collection of Technical Papers - 11th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference · January 1, 2006 Presented is a technique for developing a nonlinear reduced order model of a computational fluid dynamic solver. The method is based on a Taylor series expansion of a frequency domain harmonic balance computational fluid dynamic solver residual. The comput ... Full text Cite

Nonlinear analysis of unsteady flows in multistage turbomachines using the harmonic balance technique

Conference Collection of Technical Papers - 44th AIAA Aerospace Sciences Meeting · January 1, 2006 harmonic balance technique for the analysis of two and three-dimensional linear (small-disturbance) and nonlinear unsteady flows in multistage turbomachines is presented. The present method uses a mixed time-domain/ frequency-domain approach that allows on ... Full text Cite

Nonlinear frequency-domain analysis of unsteady flows in turbomachinery with multiple excitation frequencies

Conference Collection of Technical Papers - AIAA Applied Aerodynamics Conference · January 1, 2006 A harmonic balance technique for the analysis of nonlinear unsteady flows in turbomachiney arising from several excitation sources, possibly with frequencies with irrational ratios, is presented in this paper. This method uses a mixed time-domain/frequency ... Full text Cite

Further investigation of modeling limit cycle oscillation behavior of the F-16 fighter using a harmonic balance approach

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · December 19, 2005 A computational investigation of limit cycle oscillation behavior of the F-16 fighter configuration using a nonlinear frequency-domain harmonic-balance approach is presented. The research discussed in this latest paper is a follow-on to our work presented ... Cite

Reduced order unsteady aerodynamic models and aeroelasticity

Conference 12th International Congress on Sound and Vibration 2005, ICSV 2005 · December 1, 2005 The state of reduced order modeling of unsteady aerodynamic flows for the efficient calculation of fluid-structure interaction (aeroelasticity) is discussed. Reduced order modeling is a set of conceptually novel and computationally efficient techniques for ... Cite

A modern course in aeroelasticity

Book · December 1, 2005 Cite

Multistage coupling for unsteady flows in turbomachinery

Journal Article AIAA J. (USA) · 2005 We present a three-dimensional time-linearized unsteady Euler solver for computing unsteady flows in multistage turbomachines. Using this approach, each blade row is modeled on a computational grid spanning a single blade passage. Within each blade passage ... Cite

Discrete adjoint approach for modeling unsteady aerodynamic design sensitivities

Journal Article AIAA Journal · 2005 A discrete adjoint approach is presented for computing steady and unsteady aerodynamic design sensitivities for compressible viscous flows about airfoil configurations. The nominal flow solver method is based on a harmonic balance solution technique, which ... Cite

Computational models for nonlinear aeroelasticity

Conference 43rd AIAA Aerospace Sciences Meeting and Exhibit - Meeting Papers · January 1, 2005 Two distinctly different reduced-order models are formulated for fully nonlinear aeroelastic systems. The first is based on Proper Orthogonal Decomposition (POD). The velocity field is decomposed into a finite number of orthonormal modes, effecting order r ... Full text Cite

Time-linearized Navier-Stokes analysis of flutter in multistage turbomachines

Conference 43rd AIAA Aerospace Sciences Meeting and Exhibit - Meeting Papers · January 1, 2005 We present an efficient and accurate computational method for predicting three dimensional unsteady flows in multistage turbomachinery. Specifically, a time-linearized unsteady Navier-Stokes method is developed to solve the turbomachinery flutter problem, ... Full text Cite

Recent advancements in turbomachinery aeroelastic design analysis

Conference 43rd AIAA Aerospace Sciences Meeting and Exhibit - Meeting Papers · January 1, 2005 In this paper, we review some recent developments for computing unsteady aerodynamic loads associated with turbomachinery aeromechanics. In particular, we example the use of frequency domain techniques for computing unsteady flows in turbomachinery. The fr ... Full text Cite

Modeling limit cycle oscillation behavior of the F-16 fighter using a harmonic balance approach

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · December 1, 2004 A computational investigation of limit cycle oscillation behavior of the F-16 fighter configuration using a nonlinear frequency-domain harmonic-balance approach is presented. Computed limit cycle response results correlate well with experiment. Details of ... Cite

Limit-cycle oscillations of a typical airfoil in transonic flow

Journal Article Journal of Aircraft · 2004 Using an inviscid flow computational-fluid-dynamic model and a harmonic balance flow solver, a parametric investigation of how structural-inertial parameters and freestream Mach number of a transonic flow affect the limit-cycle oscillation characteristics ... Cite

Transonic limit cycle oscillation analysis using reduced order aerodynamic models

Journal Article Journal of Fluids and Structures · 2004 Limit cycle oscillations have been observed in flight operations of modern aircraft, wind tunnel experiments and mathematical models. Both fluid and structural nonlinearities are thought to contribute to these phenomena. With recent advances in reduced ord ... Full text Link to item Cite

Modeling viscous transonic limit-cycle oscillation behavior using a harmonic balance approach

Journal Article Journal of Aircraft · 2004 Presented is a harmonic-balance computational fluid dynamic approach for modeling limit-cycle oscillation behavior of aeroelastic airfoil configurations in a viscous transonic flow. For the NLR 7301 airfoil configuration studied, accounting for viscous eff ... Cite

Improved understanding of transonic flutter: A three-parameter flutter surface

Journal Article Journal of Aircraft · 2004 An understanding of transonic flutter is often critical for high-speed aircraft development. A presentation of the transonic flutter velocity as a function of the Mach number and mass ratio is shown here to provide many advantages. Such a presentation offe ... Cite

Frequency domain techniques for complex and nonlinear flows in turbomachinery

Conference 33rd AIAA Fluid Dynamics Conference and Exhibit · December 1, 2003 In this paper, we review frequency domain techniques for computing unsteady flows in turbomachinery. The frequency domain approaches, which can be used to model both small-disturbance and nonlinear time periodic flows, are computationally very efficient, t ... Cite

A discrete adjoint approach for modeling unsteady aerodynamic design sensitivities

Conference 41st Aerospace Sciences Meeting and Exhibit · December 1, 2003 Presented is a discrete adjoint approach for computing steady and unsteady aerodynamic design sensitivities for compressible viscous flows about airfoil configurations. The nominal flow solver method is based on a harmonic balance solution technique, which ... Cite

A harmonic balance approach for modeling nonlinear aeroelastic behavior of wings in transonic viscous flow

Conference 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference · December 1, 2003 Presented is a frequency-domain harmonic-balance (HB) computational fluid dynamic (CFD) approach for modeling flutter onset and limit cycle oscillation (LCO) behavior of viscous transonic aeroelastic wing configurations. The AGARD 445.6 transonic wing conf ... Cite

Modeling limit cycle oscillations for an NLR 7301 airfoil aeroelastic configuration including correlation with experiment

Conference 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference · December 1, 2003 Presented is an investigation into the modeling of limit cycle oscillation (LCO) behavior of an experimental transonic airfoil aeroelastic configuration using a frequency-domain harmonic-balance (HB) computational fluid dynamic (CFD) approach. The aeroelas ... Cite

A harmonic balance approach for modeling nonlinear aeroelastic behavior of wings in transonic viscous flow

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · August 28, 2003 Presented is a frequency-domain harmonic-balance (HB) computational fluid dynamic (CFD) approach for modeling flutter onset and limit cycle oscillation (LCO) behavior of viscous transonic aeroelastic wing configurations. The AGARD 445.6 transonic wing conf ... Cite

A discrete adjoint approach for modeling unsteady aerodynamic design sensitivities

Conference 41st Aerospace Sciences Meeting and Exhibit · January 1, 2003 Presented is a discrete adjoint approach for computing steady and unsteady aerodynamic design sensitivities for compressible viscous flows about airfoil configurations. The nominal flow solver method is based on a harmonic balance solution technique, which ... Full text Cite

A harmonic balance approach for modeling nonlinear aeroelastic behavior of wings in transonic viscous flow

Conference 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference · January 1, 2003 Presented is a frequency-domain harmonic-balance (HB) computational fluid dynamic (CFD) approach for modeling flutter onset and limit cycle oscillation (LCO) behavior of viscous transonic aeroelastic wing configurations. The AGARD 445.6 transonic wing conf ... Full text Cite

Blade excitation by aerodynamic instabilities - A compressor blade study

Conference American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI · 2003 In this paper, we investigate non-synchronous vibrations (NSV) in turbomachinery, an aeromechanic phenomenon in which rotor blades are driven by a fluid dynamic instability. Unlike flutter, a self-excited vibration in which vibrating rotor blades and the r ... Cite

Parametric study of flutter for an airfoil in inviscid transonic flow

Journal Article Journal of Aircraft · 2003 A parametric study of flutter was conducted for an airfoil in inviscid transonic flow. An inviscid computational flow dynamic harmonic balance aerodynamic-Euler-based code was used for the investigation. The computational efficiency of the time-linearized ... Cite

Three-dimensional transonic aeroelasticity using proper orthogonal decomposition-based reduced-order models

Journal Article Journal of Aircraft · 2003 The proper orthogonal decomposition (POD-) based reduced-order modeling technique for modeling unsteady frequency-domain aerodynamics is developed for a large-scale computational model of an inviscid flow transonic wing configuration. When the methodology ... Cite

Modeling limit cycle oscillations for an NLR 7301 airfoil aeroelastic configuration including correlation with experiment

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 2003 Presented is an investigation into the modeling of limit cycle oscillation (LCO) behavior of an experimental transonic airfoil aeroelastic configuration using a frequency-domain harmonic-balance (HB) computational fluid dynamic (CFD) approach. The aeroelas ... Full text Cite

Mach number influence on reduced-order models of inviscid potential flows in turbomachinery

Journal Article Trans. ASME, J. Fluids Eng. (USA) · 2002 An unsteady inviscid flow through a cascade of oscillating airfoils is investigated. An inviscid nonlinear subsonic and transonic model is used to compute the steady flow solution. Then a small amplitude motion of the airfoils about their steady flow confi ... Full text Link to item Cite

Computation of unsteady nonlinear flows in cascades using a harmonic balance technique

Journal Article AIAA Journal · 2002 A harmonic balance technique for modeling unsteady nonlinear flows in turbomachinery is presented. The analysis exploits the fact that many unsteady flows of interest in turbomachinery are periodic in time. Thus, the unsteady flow conservation variables ma ... Cite

Nonlinear inviscid aerodynamic effects on transonic divergence, flutter, and limit-cycle oscillations

Journal Article AIAA Journal · 2002 By the use of a state-of-the-art computational fluid dynamic (CFD) method to model nonlinear steady and unsteady transonic flows in conjunction with a linear structural model, an investigation is made into how nonlinear aerodynamics can effect the divergen ... Cite

A harmonic balance approach for modeling three-dimensional nonlinear unsteady aerodynamics and aeroelasticity

Conference ASME International Mechanical Engineering Congress and Exposition, Proceedings · January 1, 2002 Presented is a frequency domain harmonic balance (HB) technique for modeling nonlinear unsteady aerodynamics of three-dimensional transonic inviscid flows about wing configurations. The method can be used to model efficiently nonlinear unsteady aerodynamic ... Full text Cite

Modeling viscous transonic limit cycle oscillation behavior using a harmonic balance approach

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 2002 Presented is a harmonic-balance (HB) computational fluid dynamic (CFD) approach for modeling limit cycle oscillation (LCO) behavior of aeroelastic airfoil configurations in a viscous transonic flow. For the NLM 7301 airfoil configuration studied, accountin ... Full text Cite

A parameter study of transonic airfoil flutter and limit cycle oscillation behavior

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 2002 A parameter study of transonic airfoil flutter and limit cycle oscillation (LCO) behavior was presented. The effect of structural parameters and freestream Mach number of a transonic flow on the flutter and LCO was found out using inviscid computational fl ... Cite

A rational engineering analysis of the efficiency of flapping flight

Conference FIXED AND FLAPPING WING AERODYNAMICS FOR MICRO AIR VEHICLE APPLICATIONS · January 1, 2002 Link to item Cite

Transonic limit cycle oscillation analysis using reduced order aerodynamic models

Conference 19th AIAA Applied Aerodynamics Conference · December 1, 2001 Limit cycle oscillations have been observed in flight operations of modern aircraft, wind tunnel experiments and mathematical models. Both fluid and structural nonlinearities are thought to contribute to these phenomena. With recent advances in reduced ord ... Cite

Three-Dimensional transonic Aeroelasticity using proper orthogonal decomposition based reduced order models

Conference 19th AIAA Applied Aerodynamics Conference · December 1, 2001 The proper orthogonal decomposition (POD) based reduced order modeling (ROM) technique for modeling unsteady frequency domain aerodynamics is developed for a large scale computational model of an inviscid flow transonic wing configuration. Using the method ... Cite

Nonlinear inviscid aerodynamic effects on transonic divergence, flutter and limit cycle oscillations

Conference 19th AIAA Applied Aerodynamics Conference · December 1, 2001 Using a state of the art computational fluid dynamic (CFD) method to model nonlinear steady and unsteady transonic flows in conjunction with a linear structural model, an investigation is made into how nonlinear aerodynamics can effect the divergence, flut ... Cite

A static/dynamic correction approach for reduced-order modeling of unsteady aerodynamics

Conference 39th Aerospace Sciences Meeting and Exhibit · December 1, 2001 Presented is a newly devised static/dynamic correction approach for eigenvector expansion based reduced-order modeling (ROM). When compared to the fundamental Ritz ROM formulation, along with the static and multiple static correction ROM approaches, the te ... Cite

Sensitivity analysis of unsteady inviscid flow through turbomachinery cascades

Conference AIAA Journal · January 1, 2001 We present a novel sensitivity analysis for predicting the effect of airfoil shape on the unsteady aerodynamic and aeroacoustic response of turbomachinery blading. The nominal steady and unsteady flow in a cascade of turbomachinery blades is modeled using ... Full text Cite

A parametric analysis of reduced order models of potential flows in turbomachinery using proper orthogonal decomposition

Conference Proceedings of the ASME Turbo Expo · January 1, 2001 An unsteady inviscid flow through a cascade of oscillating airfoils is investigated. An inviscid nonlinear subsonic and transonic model is used to compute the steady flow solution. Then a small amplitude motion of the airfoils about their steady flow confi ... Full text Cite

Three-Dimensional transonic Aeroelasticity using proper orthogonal decomposition based reduced order models

Conference 19th AIAA Applied Aerodynamics Conference · January 1, 2001 The proper orthogonal decomposition (POD) based reduced order modeling (ROM) technique for modeling unsteady frequency domain aerodynamics is developed for a large scale computational model of an inviscid flow transonic wing configuration. Using the method ... Full text Cite

Transonic limit cycle oscillation analysis using reduced order aerodynamic models

Conference 19th AIAA Applied Aerodynamics Conference · January 1, 2001 Limit cycle oscillations have been observed in flight operations of modern aircraft, wind tunnel experiments and mathematical models. Both fluid and structural nonlinearities are thought to contribute to these phenomena. With recent advances in reduced ord ... Full text Cite

Nonlinear inviscid aerodynamic effects on transonic divergence, flutter and limit cycle oscillations

Conference 19th AIAA Applied Aerodynamics Conference · January 1, 2001 Using a state of the art computational fluid dynamic (CFD) method to model nonlinear steady and unsteady transonic flows in conjunction with a linear structural model, an investigation is made into how nonlinear aerodynamics can effect the divergence, flut ... Full text Cite

A static/dynamic correction approach for reduced-order modeling of unsteady aerodynamics

Conference 39th Aerospace Sciences Meeting and Exhibit · January 1, 2001 Presented is a newly devised static/dynamic correction approach for eigenvector expansion based reduced-order modeling (ROM). When compared to the fundamental Ritz ROM formulation, along with the static and multiple static correction ROM approaches, the te ... Full text Cite

Modeling of fluid-structure interaction

Journal Article Annual Review of Fluid Mechanics · 2001 The interaction of a flexible structure with a flowing fluid in which it is submersed or by which it is surrounded gives rise to a rich variety of physical phenomena with applications in many fields of engineering, for example, the stability and response o ... Full text Link to item Cite

Three-dimensional transonic aeroelasticity using proper orthogonal decomposition based reduced order models

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 2001 The proper orthogonal decomposition (POD) based reduced order modeling (ROM) technique for modeling unsteady frequency domain aerodynamics is developed for a large scale computational model of an inviscid flow transonic wing configuration. Using the method ... Cite

Transonic limit cycle oscillation analysis using reduced order aerodynamic models

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 2001 Limit cycle oscillations have been observed in flight operations of modern aircraft, wind tunnel experiments and mathematical models. Both fluid and structural nonlinearities are thought to contribute to these phenomena. With recent advances in reduced ord ... Cite

Reduced-order models of unsteady viscous flows in turbomachinery using viscous-inviscid coupling

Journal Article Journal of Fluids and Structures · January 1, 2001 The proper orthogonal decomposition technique is applied in the frequency domain to obtain a reduced-order model of the flow in a turbomachinery cascade. The flow is described by an inviscid-viscous interaction model where the inviscid part is described by ... Full text Cite

Nonlinear inviscid aerodynamic effects on transonic divergence, flutter and limit cycle oscillations

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 2001 Using a state of the art computational fluid dynamic (CFD) method to model nonlinear steady and unsteady transonic flows in conjunction with a linear structural model, an investigation is made into how nonlinear aerodynamics can effect the divergence, flut ... Cite

Sensitivity analysis of unsteady inviscid flow through turbomachinery cascades

Journal Article 38th Aerospace Sciences Meeting and Exhibit · December 1, 2000 In this paper, we present a novel sensitivity analysis for predicting the effect of airfoil shape on the unsteady aerodynamic and aeroacoustic response of turbomachinery blading. The nominal steady and unsteady flow in a cascade of turbomachinery blades is ... Cite

Sensitivity analysis of unsteady inviscid flow through turbomachinery cascades

Conference 38th Aerospace Sciences Meeting and Exhibit · January 1, 2000 In this paper, we present a novel sensitivity analysis for predicting the effect of airfoil shape on the unsteady aerodynamic and aeroacoustic response of turbomachinery blading. The nominal steady and unsteady flow in a cascade of turbomachinery blades is ... Full text Cite

Time-linearized Navier-Stokes analysis of stall flutter

Journal Article Journal of Turbomachinery, Transactions of the ASME · 2000 A computational method for predicting unsteady viscous flow through two-dimensional cascades accurately and efficiently is presented. The method is intended to predict the onset of the aeroelastic phenomenon of stall flutter. In stall flutter, viscous effe ... Full text Link to item Cite

Eigenmode analysis and reduced-order modeling of unsteady transonic potential flow around airfoils

Journal Article Journal of Aircraft · 2000 An eigenmode analysis and reduced-order models of the unsteady transonic aerodynamic flow around isolated airfoils are presented. The unsteady flow is modeled using the time-linearized frequency-domain unsteady transonic full potential equation. The full p ... Cite

Proper orthogonal decomposition technique for transonic unsteady aerodynamic flows

Journal Article AIAA Journal · 2000 A new method for constructing reduced-order models (ROM) of unsteady small-disturbance flows is presented. The reduced-order models are constructed using basis vectors determined from the proper orthogonal decomposition (POD) of an ensemble of small-distur ... Cite

Reduced-order models of unsteady transonic viscous flows in turbomachinery

Journal Article Journal of Fluids and Structures · 2000 The proper orthogonal decomposition (POD) technique is applied in the frequency domain to obtain a reduced-order model of the unsteady flow in a transonic turbomachinery cascade of oscillating blades. The flow is described by a inviscid - viscous model, i. ... Full text Link to item Cite

A time-linearized Navier-Stokes analysis of stall flutter

Conference Proceedings of the ASME Turbo Expo · January 1, 1999 A computational method for accurately and efficiently predicting unsteady viscous flow through two-dimensional cascades is presented. The method is intended to predict the onset of the aeroelastic phenomenon of stall flutter. In stall flutter, viscous effe ... Full text Cite

Reduced-order modelling of unsteady small-disturbance flows using a frequency-domain proper orthogonal decomposition technique

Conference 37th Aerospace Sciences Meeting and Exhibit · January 1, 1999 © 1999 by Kenneth C. Hall, Jeffrey P. Thomas, and Earl H. Dowell.A new method for constructing reduced-order models (ROM) of unsteady small-disturbance flows is presented. The reduced-order models are constructed using basis vectors determined from the pro ... Cite

Reduced-order modelling of unsteady small-disturbance flows using a frequency-domain proper orthogonal decomposition technique

Conference 37th Aerospace Sciences Meeting and Exhibit · January 1, 1999 A new method for constructing reduced-order models (ROM) of unsteady small-disturbance flows is presented. The reduced-order models are constructed using basis vectors determined from the proper orthogonal decomposition (POD) of an ensemble of small-distur ... Full text Cite

REDUCED ORDER MODELS OF VISCOUS FLOWS IN TURBOMACHINERY USING PROPER ORTHOGONAL DECOMPOSITION

Conference ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) · January 1, 1999 The proper orthogonal decomposition technique is applied in the frequency domain to obtain reduced order models (ROM) of the flow in a cascade of airfoils. The flow is described by a inviscid-viscous interaction model where the inviscid part is described b ... Full text Cite

Reduced order models of viscous flows in turbomachinery using proper orthogonal decomposition

Conference American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED · 1999 The proper orthogonal decomposition technique is applied in the frequency domain to obtain reduced order models (ROM) of the flow in a cascade of airfoils. The flow is described by a inviscid-viscous interaction model where the inviscid part is described b ... Cite

Limit Cycle Oscillations of a Cantilevered Wing in Low Subsonic Flow

Journal Article AIAA Journal · January 1, 1999 A nonlinear, aeroelaslic analysis of a low-aspect, rectangular wing modeled as a plate of constant thickness demonstrates that limit cycle oscillations of the order of the plate thickness are possible. The structural nonlinearity arises from double bending ... Full text Cite

Reduced order models in unsteady aerodynamics

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 1999 A review is given on the status of reduced order modeling of unsteady aerodynamic systems. Starting with either a time domain or frequency domain computational fluid dynamics (CFD) analysis of unsteady aerodynamic flows, a large, sparse eigenvalue is solve ... Cite

Eigenmode analysis of unsteady flows about airfoils

Journal Article Journal of Computational Physics · December 10, 1998 We present a reduced-order modelling technique for analyzing the unsteady subsonic aerodynamic flow about isolated airfoils. To start, we model the flow using the time-linearized full potential equation. The linearized potential equation is discretized on ... Full text Cite

Coupled mode analysis of unsteady multistage flows in turbomachinery

Journal Article Journal of Turbomachinery, Transactions of the ASME · 1998 A computational method is presented for predicting the unsteady aerodynamic response of a vibrating blade row that is part of a multistage turbomachine. Most current unsteady aerodynamic theories model a single blade row isolated in an infinitely long duct ... Cite

Power requirements for large-amplitude flapping flight

Journal Article Journal of Aircraft · 1998 In this paper, a method is presented for computing the circulation distribution along the span of a flapping wing that minimizes the power required to generate a prescribed lift and thrust. The power is composed of three parts: useful thrust power, induced ... Cite

Reduced-order modeling of unsteady viscous flow in a compressor cascade

Journal Article AIAA Journal · January 1, 1998 A simultaneously coupled viscous-inviseid interaction (VII) analysis is used to model the unsteady viscous separated flow through a subsonic compressor. The inner viscous flow around the airfoil and in the wake is modeled using a finite difference discreti ... Full text Cite

Eigenmode analysis of unsteady viscous flows in turbomachinery cascades

Conference UNSTEADY AERODYNAMICS AND AEROELASTICITY OF TURBOMACHINES · January 1, 1998 Link to item Cite

Reduced order aerodynamic modeling of how to make CFD useful to an aeroelastician

Conference American Society of Mechanical Engineers, Aerospace Division (Publication) AD · December 1, 1997 In this article, we review the status of reduced order modeling of unsteady aerodynamic systems. Reduced order modeling is a conceptually novel and computationally efficient technique for computing unsteady flow about isolated airfoils, wings, and turbomac ... Cite

Coupled mode analysis of unsteady multistage flows in turbomachinery

Conference American Society of Mechanical Engineers (Paper) · December 1, 1997 A `coupled mode' analysis is useful in predicting the unsteady aerodynamic response of vibrating multistage turbomachine blades. Using this approach, the coupling between the blade rows is modeled using a subset of spinning modes. The blade rows are repres ... Cite

Power requirements for large-amplitude flapping flight

Conference 35th Aerospace Sciences Meeting and Exhibit · January 1, 1997 © 1997 by Kenneth C. Hall, Steven A. Pigott, and Steven R. Hall.In this paper, a method is presented for computing the circulation distribution along the span of a flapping wing that minimizes the power required to generate a prescribed lift and thrust. Th ... Cite

A coupled mode analysis of unsteady multistage flows in turbomachinery

Conference Proceedings of the ASME Turbo Expo · January 1, 1997 A computational method is presented for predicting the unsteady aerodynamic response of a vibrating blade row which is part of a multistage turbomachine. Most current unsteady aerodynamic theories model a single blade row isolated in an infinitely long duc ... Full text Cite

Power requirements for large-amplitude flapping flight

Conference 35th Aerospace Sciences Meeting and Exhibit · January 1, 1997 In this paper, a method is presented for computing the circulation distribution along the span of a flapping wing that minimizes the power required to generate a prescribed lift and thrust. The power is composed of three parts: The useful thrust power, and ... Cite

Reduced Order Aerodynamic Modeling of How to Make CFD Useful to An Aeroelastician

Conference ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) · January 1, 1997 In this article, we review the status of reduced order modeling of unsteady aerodynamic systems. Reduced order modeling is a conceptually novel and computationally efficient technique for computing unsteady flow about isolated airfoils, wings, and turbomac ... Full text Cite

Influence of neighboring blade rows on the unsteady aerodynamic response of cascades

Journal Article Journal of Turbomachinery, Transactions of the ASME · 1997 In this paper, we present an analysis of the unsteady aerodynamic response of cascades due to incident gusts (the forced response problem) or blade vibration (the flutter problem) when the cascade is part of a multistage fan, compressor, or turbine. Most c ... Cite

Eigenmode analysis in unsteady aerodynamics: reduced order models

Journal Article Applied Mechanics Reviews · 1997 In this article, we review the status of reduced order modeling of unsteady aerodynamic systems. Reduced order modeling is a conceptually novel and computationally efficient technique for computing unsteady flow about isolated airfoils, wings, and turbomac ... Cite

Reduced order modelling of unsteady viscous flow in a compressor cascade

Conference 32nd Joint Propulsion Conference and Exhibit · January 1, 1996 © 1996, American Institute of Aeronautics and Astronautics, Inc. A simultaneously coupled inviscid-viscous interaction (IVI) analysis is used to model the unsteady viscous separated flow through a subsonic compressor. The inner viscous flow around the airf ... Cite

Reduced order modelling of unsteady viscous flow in a compressor cascade

Conference 32nd Joint Propulsion Conference and Exhibit · January 1, 1996 A simultaneously coupled inviscid-viscous interaction (IVI) analysis is used to model the unsteady viscous separated flow through a subsonic compressor. The inner viscous flow around the airfoil and in the wake is modelled using a finite difference discret ... Full text Cite

Minimum induced power requirements for flapping flight

Journal Article Journal of Fluid Mechanics · 1996 The Betz criterion for minimum induced loss is used to compute the optimal circulation distribution along the span of flapping wings in fast forward flight. In particular, we consider the case where flapping motion is used to generate both lift (weight sup ... Cite

Sensitivity analysis of the aeroacoustic response of turbomachinery blade rows

Journal Article AIAA Journal · January 1, 1996 A method for computing the change or sensitivity of the aeroacoustic response of a cascade to small changes in airfoil and cascade geometry is presented. The steady flow is modeled by the full potential equation, which is discretized using a variational fi ... Full text Cite

A viscous-inviscid model of unsteady small-disturbance flows in cascades

Conference 31st Joint Propulsion Conference and Exhibit · January 1, 1995 A simultaneously coupled viscous-inviscid (IVI) procedure for computing the unsteady flow associated with the onset of stall flutter in turbomachinery cascades is presented. Using this method, the flow is divided into two parts: a viscous flow near the air ... Cite

Sensitivity analysis of the aeroacoustic response of turbomachinery blade rows

Conference 33rd Aerospace Sciences Meeting and Exhibit · January 1, 1995 A method for computing the sensitivity of the aeroacoustic response of a cascade to small changes in airfoil and cascade geometry is presented. The steady flow is modeled by the full potential equation, which is discretized using a variational finite eleme ... Full text Cite

A numerical model of the onset of stall flutter in cascades

Conference Proceedings of the ASME Turbo Expo · January 1, 1995 In this paper, we present a computational fluid dynamic model of the unsteady flow associated with the onset of stall flutter in turbomachinery cascades. The unsteady flow is modeled using the laminar Navier-Stokes equations. We assume that the unsteadines ... Full text Cite

The influence of neighboring blade rows on the unsteady aerodynamic response of cascades

Conference Proceedings of the ASME Turbo Expo · January 1, 1995 In this paper, we present an analysis of the unsteady aerodynamic response of cascades due to incident gusts (the forced response problem) or blade vibration (the flutter problem) when the cascade is part of a multistage fan, compressor, or turbine. Most c ... Full text Cite

Sensitivity analysis of unsteady aerodynamic loads in cascades

Journal Article AIAA Journal · January 1, 1995 A method for computing the effect perturbations in the shape of airfoils in a cascade have on the steady and unsteady flow through the cascade is presented. First, the full potential equation is used to describe the behavior of the nonlinear steady flow an ... Full text Cite

Numerical model of the onset of stall flutter in cascades

Conference American Society of Mechanical Engineers (Paper) · January 1, 1995 In this paper, we present a computational fluid dynamic model of the unsteady flow associated with the onset of stall flutter in turbomachinery cascades. The unsteady flow is modeled using the laminar Navier-Stokes equations. We assume that the unsteadines ... Cite

Influence of neighboring blade rows on the unsteady aerodynamic response of cascades

Conference American Society of Mechanical Engineers (Paper) · January 1, 1995 An analysis of the unsteady aerodynamic response of cascade due to incident gusts or blade vibration when the cascade is part of a multistage fan, compressor, or turbine is presented. Since most of the current unsteady aerodynamic models assume the cascade ... Cite

Computation of steady and unsteady viscous flows using a simultaneously coupled inviscid-viscous interaction technique

Journal Article Journal of Fluids and Structures · January 1, 1995 An interacting viscous-inviscid method for efficiently computing steady and unsteady low Mach number viscous flows with separation is presented. The inviscid region is modeled using a finite element discretization of the full potential equation. The viscou ... Full text Cite

A reduced order model of unsteady flows in turbomachinery

Journal Article Journal of Turbomachinery · January 1, 1995 A novel technique for computing unsteady flows about turbomachinery cascades is presented. Starting with a frequency domain CFD description of unsteady aerodynamic flows, we form a large, sparse, generalized, non-Hermitian eigenvalue problem that describes ... Full text Cite

Reduced order modeling of unsteady flows about airfoils

Conference American Society of Mechanical Engineers, Aerospace Division (Publication) AD · December 1, 1994 We present a reduced order modeling technique for analyzing the unsteady aerodynamic flow about isolated airfoils. To start, we model the flow using the time-linearized full potential equation. The linearized potential equation is discretized on a computat ... Cite

Eigenanalysis of unsteady flows about airfoils, cascades, and wings

Conference Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · December 1, 1994 A general technique for constructing reduced order models of unsteady aerodynamic flows about two-dimensional isolated airfoils, cascades of airfoils, and three-dimensional wings was developed. The technique was applied to an unsteady incompressible vortex ... Cite

Reduced order model of unsteady flows in turbomachinery

Conference American Society of Mechanical Engineers (Paper) · January 1, 1994 A novel technique for computing unsteady flows about turbomachinery cascades is presented. Starting with a frequency domain CFD description of unsteady aerodynamic flows, we form a large, sparse, generalized, non-Hermitian eigenvalue problem which describe ... Cite

Linearized euler analysis of unsteady transonic flows in turbomachinery

Journal Article Journal of Turbomachinery, Transactions of the ASME · 1994 A computational method for efficiently predicting unsteady transonic flows in two-and three-dimensional cascades is presented. The unsteady flow is modeled using a linearized Euler analysis whereby the unsteady flow field is decomposed into a nonlinear mea ... Cite

Helicopter rotor lift distributions for minimum-induced power loss

Journal Article Journal of Aircraft · January 1, 1994 A method is described for solving the minimum-induced loss (MIL) rotor design problem. First, the generalized Betz condition for MIL rotors is developed. Because the resulting lift distributions would generally exceed the maximum blade lift coefficient on ... Full text Cite

Eigenanalysis of unsteady flows about airfoils, cascades, and wings

Journal Article AIAA Journal · January 1, 1994 A general technique for constructing reduced order models of unsteady aerodynamic flows about twodimensional isolated airfoils, cascades of airfoils, and three-dimensional wings is developed. The starting point is a time domain computational model of the u ... Full text Cite

A reduced order model of unsteady flows in turbomachinery

Conference Proceedings of the ASME Turbo Expo · January 1, 1994 A novel technique for computing unsteady flows about turbomachinery cascades is presented. Starting with a frequency domain CFD description of unsteady aerodynamic flows, we form a large, sparse, generalized, non-Hermitian eigenvalue problem which describe ... Full text Cite

Linearized Euler analysis of unsteady transonic flows in turbomachinery

Conference American Society of Mechanical Engineers (Paper) · January 1, 1993 A computational method for efficiently predicting unsteady transonic flows in two - and three-dimensional cascades is presented. The unsteady flow is modelled using a linearized Euler analysis whereby the unsteady flow field is decomposed into a nonlinear ... Cite

A linearized euler analysis of unsteady transonic flows in turbomachinery

Conference ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition, GT 1993 · January 1, 1993 A computational method for efficiently predicting unsteady transonic flows in two- and three-dimensional cascades is presented. The unsteady flow is modelled using a linearized Euler analysis whereby the unsteady flow field is decomposed into a nonlinear m ... Full text Cite

Deforming grid variational principle for unsteady small disturbance flows in cascades

Journal Article AIAA Journal · January 1, 1993 A variational method for computing unsteady subsonic flows in turbomachinery blade rows is presented. A variational principle that describes the harmonic small disturbance behavior of the full potential equations about a nonlinear mean flow is developed. I ... Full text Cite

Calculation of three-dimensional unsteady flows in turbomachinery using the linearized harmonic Euler equations

Journal Article Journal of Turbomachinery, Transactions of the ASME · 1993 An efficient three-dimensional Euler analysis of unsteady flows in turbomachinery is presented. The unsteady flow is modeled as the sum of a steady or mean flow field plus a harmonically varying small perturbation flow. The linearized Euler equations, whic ... Cite

Linearized euler predictions of unsteady aerodynamic loads in cascades

Journal Article AIAA Journal · January 1, 1993 A linearized Euler solver for calculating unsteady flows in turbomachinery blade rows due to both incident gusts and vibratory blade motion is presented. Using the linearized Euler technique, one decomposes the flow into a mean (or steady) flow plus an uns ... Full text Cite

Calculation of three-dimensional unsteady flows in turbomachinery using the linearized harmonic Euler equations

Conference ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition, GT 1992 · January 1, 1992 An efficient three-dimensional Euler analysis of unsteady flows in turbomachinery is presented. The unsteady flow is modelled as the sum of a steady or mean flow field plus a harmonically varying small perturbation flow. The linearized Euler equations, whi ... Full text Cite

Calculation of Three-Dimensional Unsteady Flows in Turbomachinery Using the Linearized Harmonic Euler Equations

Conference ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition, GT 1992 · January 1, 1992 An efficient three-dimensional Euler analysis of unsteady flows in turbomachinery is presented. The unsteady flow is modelled as the sum of a steady or mean flow field plus a harmonically varying small perturbation flow. The linearized Euler equations, whi ... Full text Cite

Gust response analysis for cascades operating in nonuniform mean flows

Journal Article AIAA Journal · January 1, 1991 The unsteady aerodynamic response of a subsonic cascade subjected to entropic, vortical, and acoustic gusts is analyzed. Field equations for the first-order unsteady perturbation are obtained by linearizing the time-dependent mass, momentum, and energy con ... Full text Cite

Calculation of unsteady flows in turbomachinery using the linearizedEuler equations

Journal Article AIAA Journal · January 1, 1989 A method for calculating unsteady flows in cascades is presented. The model, which is based on the linearized unsteady Euler equations, accounts for blade loading, blade geometry, shock motion, and wake motion. Assuming that the unsteadiness in the flow is ... Full text Cite

Optimization and mechanisms of mistuning in cascades

Journal Article Journal of Engineering for Gas Turbines and Power · January 1, 1985 An inverse design procedure has been developed for the optimum mistuning of a high bypass ratio shroudless fan. The fan is modeled as a cascade of blades, each with a single torsional degree of freedom. Linearized supersonic aerodynamic theory is used to c ... Full text Cite

OPTIMIZATION AND MECHANISMS OF MISTUNING IN CASCADES.

Conference American Society of Mechanical Engineers (Paper) · January 1, 1984 Cite

OPTIMIZATION AND MECHANISMS OF MISTUNING IN CASCADES.

Conference American Society of Mechanical Engineers (Paper) · January 1, 1984 Cite

Accurate centroid tracking

Conference Proceedings of SPIE - The International Society for Optical Engineering · August 9, 1983 The object of this work was to develop analytical tools for describing errors associated with mosaic array centroiding. As an example of a current problem, a Monte Carlo simulation of a point source tracking problem was implemented. Then for a given noise ... Full text Cite

Fast estimation of unsteady flows in turbomachinery at multiple interblade phase angles

Journal Article AIAA J. (USA) Time-linearized computational fluid dynamic (CFD) models for the computation of unsteady flows in turbomachinery are now used routinely in the design and analysis of turbomachinery blade rows, particularly to predict the onset of flutter. A typical flutter ... Full text Link to item Cite