Scholars@Duke
Christopher Douglas

Christopher Douglas

Assistant Professor in the Thomas Lord Department of Mechanical Engineering and Materials Science
Thomas Lord Department of Mechanical Engineering and Materials Science

Selected Publications

Onset of global instability in a premixed annular V-flame

Journal Article Journal of Fluid Mechanics · October 28, 2024 We investigate self-excited axisymmetric oscillations of a lean premixed methane–air V-flame in a laminar annular jet. The flame is anchored near the rim of the centrebody, forming an inverted cone, while the strongest vorticity is concentrated along the o ... Full text Cite

Resolvent analysis of swirling turbulent jets

Journal Article Theoretical and Computational Fluid Dynamics · October 1, 2024 Abstract: This study explores coherent structures in a swirling turbulent jet. Stationary axisymmetric solutions of the Reynolds–Averaged Navier–Stokes equations at Re=200,000 were obtained using an open source computational fluid dynamics code and the Spa ... Full text Cite

A balanced outflow boundary condition for swirling flows

Journal Article Theoretical and Computational Fluid Dynamics · August 1, 2024 In open flow simulations, the dispersion characteristics of disturbances near synthetic boundaries can lead to unphysical boundary scattering interactions that contaminate the resolved flow upstream by propagating numerical artifacts back into the domain i ... Full text Cite

Pollutant Emissions Reporting and Performance Considerations for Ammonia-Blended Fuels in Gas Turbines

Journal Article Journal of Engineering for Gas Turbines and Power · January 1, 2024 To limit climate change and promote energy security, there is widespread interest toward transitioning existing fossil fueled combustion systems to sustainable, alternative fuels such as hydrogen (H2) and ammonia (NH3) without negatively impacting air qual ... Full text Cite

The role of hydrodynamic shear in the thermoacoustic response of slit flames

Journal Article Proceedings of the Combustion Institute · January 1, 2024 Short wavelength hydrodynamic perturbations excited by long wavelength acoustics can wrinkle the front of acoustically compact flames, perturb the heat release rate, and generate sound, thereby closing a thermoacoustic feedback loop. One important conversi ... Full text Cite

Resolvent analysis of subsonic jets: trapped modes and resonance mechanisms

Conference 30th AIAA/CEAS Aeroacoustics Conference, 2024 · January 1, 2024 Trapped acoustic waves in the potential core of compressible jets have been shown to participate in a variety of resonance phenomena. To further investigate these, a global resolvent-based approach is considered and applied to a subsonic jet flow at Ma = 0 ... Full text Cite

Flash-back, blow-off, and symmetry breaking of premixed conical flames

Journal Article Combustion and Flame · December 1, 2023 Hydrodynamic and thermal-diffusive effects subject premixed flames to intrinsic instabilities that strongly influence their shape and propagation/stabilization characteristics. However, the interaction and coupling of intrinsic flame dynamics with backgrou ... Full text Cite

POLLUTANT EMISSIONS REPORTING AND PERFORMANCE CONSIDERATIONS FOR AMMONIA-BLENDED FUELS IN GAS TURBINES

Conference Proceedings of the ASME Turbo Expo · January 1, 2023 To limit climate change and promote energy security, there is widespread interest towards transitioning existing fossil fueled combustion systems to sustainable, alternative fuels such as hydrogen (H2) and ammonia (NH3) without negatively impacting air qua ... Full text Cite

Pollutant Emissions Reporting and Performance Considerations for Hydrogen-Hydrocarbon Fuels in Gas Turbines

Journal Article Journal of Engineering for Gas Turbines and Power · September 1, 2022 Hydrogen (H2) fuel for gas turbines is a promising approach for long duration storage and dispatchable utilization of intermittent renewable power. A major global discussion point, however, is the potential air quality impact of hydrogen combustion associa ... Full text Cite

Confinement effects in laminar swirling jets

Journal Article Journal of Fluid Mechanics · August 25, 2022 This paper explores the effect of axial and radial confinement on the flow topology of laminar swirling jets. Its objective is to provide a unifying perspective toward swirling jet mechanics that connects earlier reports across a variety of confined and un ... Full text Cite

Dynamics and bifurcations of laminar annular swirling and non-swirling jets

Journal Article Journal of Fluid Mechanics · July 25, 2022 This paper presents bifurcation analyses characterising the nonlinear dynamics of fully developed laminar annular jets with respect to the centrebody diameter, Reynolds number, and swirl ratio. Similar flows appear in numerous applications and feature a vi ... Full text Cite

Permuted proper orthogonal decomposition for analysis of advecting structures

Journal Article Journal of Fluid Mechanics · January 10, 2022 Flow data are often decomposed using proper orthogonal decomposition (POD) of the space-time separated form, which targets spatially correlated flow structures in an optimal manner. This paper analyses permuted POD (PPOD), which decomposes data as, where i ... Full text Cite

POLLUTANT EMISSIONS REPORTING AND PERFORMANCE CONSIDERATIONS FOR HYDROGEN–HYDROCARBON FUELS IN GAS TURBINES

Conference Proceedings of the ASME Turbo Expo · January 1, 2022 Hydrogen (H2) fuel for gas turbines is a promising approach for long duration storage and dispatchable utilization of intermittent renewable power. A major global discussion point, however, is the potential air quality impact of hydrogen combustion associa ... Full text Cite

Forced flow response analysis of a turbulent swirling annular jet flame

Journal Article Physics of Fluids · August 1, 2021 This study of an externally forced, amplifier-type turbulent reacting swirling annular jet presents a low-order model for the flow response to transverse acoustic excitation and compares the model's predictions with experimental measurements. The model is ... Full text Cite

Nonlinear dynamics of fully developed swirling jets

Journal Article Journal of Fluid Mechanics · January 1, 2021 This paper characterises the steady and time-periodic behaviour of swirling jets using numerical bifurcation analysis. Its objective is to elucidate the dynamics of fully developed, unconfined, laminar swirling jets under variations in the Reynolds number ... Full text Cite

Measurements of periodic reynolds stress oscillations in a forced turbulent premixed swirling flame

Journal Article Journal of Engineering for Gas Turbines and Power · January 1, 2019 This work is motivated by the thermoacoustic instability challenges associated with ultralow emissions gas turbine (GT) combustors. It demonstrates the first use of high-speed dual-plane orthogonally-polarized stereoscopic-particle image velocimetry (PIV) ... Full text Cite

Axial evolution of forced helical flame and flow disturbances

Journal Article Journal of Fluid Mechanics · June 10, 2018 This paper presents 5 kHz stereo particle image velocimetry and OH planar laser induced fluorescence measurements of transversely forced swirl flames. The presence of transverse forcing on this naturally unstable flow both influences the natural instabilit ... Full text Cite

Predictions and measurements of coherent structures in a transversely-forced multi-nozzle swirl combustor

Conference AIAA Aerospace Sciences Meeting, 2018 · January 1, 2018 This work compares predictions of hydrodynamic receptivity from linear stability analysis with experimental measurements from an array of three premixed swirling flames with imposed 390 Hz transverse acoustics. The stability analysis is performed about the ... Full text Cite

Measurements of periodic Reynolds stress oscillations in a forced turbulent premixed swirling flame

Conference Proceedings of the ASME Turbo Expo · January 1, 2018 This work is motivated by the thermoacoustic instability challenges associated with ultra-low emissions gas turbine combustors. It demonstrates the first use of high-speed dual-plane orthogonally-polarized stereoscopic-particle image velocimetry and synchr ... Full text Cite

Velocity Field Response of a Forced Swirl Stabilized Premixed Flame

Conference Volume 4A: Combustion, Fuels and Emissions · June 26, 2017 This study is motivated by the necessity to develop a low order prediction approach for unsteady heat release response characteristics in lean premixed gas turbine combustors. This in turn requires an accurate description of the coherent hydrodynam ... Full text Cite

Velocity field response of a forced swirl stabilized premixed flame

Conference Proceedings of the ASME Turbo Expo · January 1, 2017 This study is motivated by the necessity to develop a low order prediction approach for unsteady heat release response characteristics in lean premixed gas turbine combustors. This in turn requires an accurate description of the coherent hydrodynamic oscil ... Full text Cite

Axial evolution of helical flame and flow disturbances in a transversely forced combustor

Conference AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting · January 1, 2017 This paper presents 5 kHz stereo PIV and OH PLIF measurements of transversely forced, triple nozzle swirl flames. This work is motivated by the problem of transverse instabilities in annular and can combustion systems. A key distinction of this problem fro ... Full text Cite

Experimental investigation and molecular dynamics simulations of impact-mode wear mechanisms in silicon micromachines with alkylsilane self-assembled monolayer films

Journal Article Journal of Applied Physics · October 28, 2015 In the current work, polycrystalline silicon microdevices are treated with a 1H,1H,2H,2H-Perfluorodecyltrichlorosilane (FDTS) self-assembled monolayer (SAM) film. Using a microelectromechanical systems-based tribometer, the adhesion characteristics of the ... Full text Cite