ConferenceJournal 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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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 ...
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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 ...
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ConferenceAIAA 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 ...
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ConferenceAIAA 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 ...
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Journal ArticleJournal 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 ...
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ConferenceProceedings 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 ...
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ConferenceProceedings 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 ...
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ConferenceProceedings 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 ...
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ConferenceJournal 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 ...
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ConferenceAnnual 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 ...
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ConferenceASME 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 ...
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Journal ArticleJournal 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 ...
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ConferenceAnnual 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 ...
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ConferenceAnnual 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 ...
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ConferenceAnnual 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 ...
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Conference54th 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 ...
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Journal ArticleAIAA 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 ...
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ConferenceAIAA 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 ...
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Journal ArticleInternational 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 ...
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ConferenceProceedings 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 ...
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ConferenceProceedings 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, ...
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ConferenceASME 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 ...
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Journal ArticleJournal 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 ...
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Conference50th 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 ...
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Conference50th 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 ...
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ConferenceProceedings 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, ...
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ConferenceProceedings 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 ...
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ConferenceProceedings 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 ...
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Journal ArticleAIAA 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 ...
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ConferenceCollection 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 ...
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Conference46th 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 ...
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Journal ArticleAnnual 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 ...
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ConferenceAnnual 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleAIAA 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 ...
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Journal ArticleJournal 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, ...
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Conference46th 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 ...
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ConferenceAnnual 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Conference19th 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 ...
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Conference47th 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 ...
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Conference47th 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 ...
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Conference47th 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 ...
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ConferenceProceedings 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 ...
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ConferenceProceedings 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 ...
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ConferenceProceedings 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 ...
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ConferenceICAS 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 ...
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ConferenceJournal 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 ...
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ConferenceCollection 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 ...
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Journal ArticleAIAA 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 ...
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Journal ArticleInternational 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 ...
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ConferenceProceedings 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 ...
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ConferenceCollection 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 ...
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ConferenceCollection 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 ...
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ConferenceProceedings 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 ...
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Journal ArticleJ. 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 ...
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Journal ArticleJournal 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 ...
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ConferenceCollection 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 ...
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ConferenceCollection 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 ...
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ConferenceCollection 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 ...
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ConferenceCollection 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 ...
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ConferenceCollection 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 ...
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Conference12th 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 ...
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Journal ArticleAIAA 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 ...
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Journal ArticleAIAA 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 ...
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Conference43rd 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 ...
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Conference43rd 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, ...
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Conference43rd 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 ...
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ConferenceCollection 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Conference33rd 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 ...
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Conference41st 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 ...
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Conference44th 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 ...
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Conference41st 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 ...
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ConferenceAmerican 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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ConferenceCollection 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 ...
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Journal ArticleTrans. 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 ...
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Journal ArticleAIAA 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 ...
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Journal ArticleAIAA 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 ...
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ConferenceASME 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 ...
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ConferenceCollection 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 ...
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ConferenceCollection 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 ...
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Conference19th 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 ...
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Conference19th 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 ...
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Conference19th 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 ...
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Conference39th 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 ...
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ConferenceAIAA 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 ...
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ConferenceProceedings 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 ...
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Conference19th 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 ...
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Conference19th 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 ...
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Conference19th 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 ...
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Conference39th 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 ...
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Journal ArticleAnnual 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 ...
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ConferenceCollection 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 ...
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ConferenceCollection 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 ...
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Journal ArticleJournal 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 ...
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ConferenceCollection 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 ...
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Journal Article38th 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 ...
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Conference38th 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleAIAA 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 ...
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Journal ArticleJournal 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. ...
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ConferenceProceedings 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 ...
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Conference37th 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 ...
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ConferenceASME 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 ...
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ConferenceAmerican 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 ...
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Journal ArticleAIAA 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 ...
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ConferenceCollection 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleAIAA 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 ...
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ConferenceAmerican 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 ...
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ConferenceAmerican 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 ...
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ConferenceProceedings 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 ...
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Conference35th 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 ...
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ConferenceASME 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleApplied 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 ...
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Conference32nd 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleAIAA 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 ...
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Conference31st 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 ...
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Conference33rd 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 ...
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ConferenceProceedings 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 ...
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ConferenceProceedings 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 ...
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Journal ArticleAIAA 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 ...
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ConferenceAmerican 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 ...
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ConferenceAmerican 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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ConferenceAmerican 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 ...
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ConferenceCollection 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 ...
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ConferenceAmerican 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleAIAA 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 ...
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ConferenceProceedings 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 ...
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ConferenceAmerican 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 ...
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ConferenceASME 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 ...
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Journal ArticleAIAA 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 ...
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Journal ArticleJournal 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 ...
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Journal ArticleAIAA 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 ...
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ConferenceASME 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 ...
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ConferenceASME 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 ...
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Journal ArticleAIAA 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 ...
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Journal ArticleAIAA 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 ...
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Journal ArticleJournal 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 ...
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ConferenceProceedings 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 ...
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Journal ArticleAIAA 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 ...
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