Article
Mechanics
Eric Won Keun Chang, Wilson Y. K. Chan, Timothy J. McIntyre, Ananthanarayanan Veeraragavan
Summary: This study provides detailed analysis of the interaction between shock waves and boundary layers in hypersonic flight, focusing on flow separation and augmented pressure/thermal loads. Experimental measurements were conducted using Mach 7 impinging-shock-flat-plate experiments, and the results showed that the shock impingement caused flow separation, increased pressure and higher heating loads. The findings of this study are consistent with previous research and indicate that separation is related to the pressure ratio and wall temperature parameter.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Shibin Cao, Jiaao Hao, Igor Klioutchnikov, Herbert Olivier, Chih-Yung Wen
Summary: Direct numerical simulations are used to study hypersonic flow over a compression ramp, revealing the formation of streamwise heat flux streaks downstream of reattachment that exhibit low-frequency unsteadiness and are non-uniformly distributed in the spanwise direction. The unsteadiness of the heat flux streaks is coupled with a pulsation of the reattachment position, and global instabilities are found to be responsible for the flow unsteadiness.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
B. Bugeat, J-Ch Robinet, J-C Chassaing, P. Sagaut
Summary: Resolvent analysis is used to study the low-frequency behavior of the laminar oblique shock wave/boundary layer interaction (SWBLI). The computed optimal gain follows a first-order low-pass filter equation, consistent with previous findings. The damping rate scales with the scale, resulting in a constant Strouhal number. The study supports the idea that the low-frequency dynamics of the SWBLI is a forced dynamics, with background perturbations continuously exciting the flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Jiyang He, Benjamin Favier, Michel Rieutord, Stephane Le Dizes
Summary: This study examines the internal shear layers generated by the longitudinal libration of the inner core in a rotating spherical shell. By using asymptotic and numerical analysis, the researchers provide insights into the behavior of these shear layers and compare the asymptotic predictions with direct numerical results. The study demonstrates that, with decreasing Ekman numbers, the agreement between the asymptotic predictions and numerical results improves.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Weibo Hu, Stefan Hickel, Bas W. van Oudheusden
Summary: The flow over a forward-facing step at Ma(infinity) = 1.7 and Re-delta 0 = 1.3718 x 10(4) was investigated using large-eddy simulation. The study compared the effects of laminar inflow and turbulent inflow on the dynamics of the shock wave/boundary layer interaction. The results showed that in the turbulent inflow case, the separation shock and Gortler-like vortices were strongly correlated with low-frequency unsteadiness.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Xin Li, Yue Zhang, Huijun Tan, Shu Sun, Hang Yu, Yi Jin, Jie Zhou
Summary: This study experimentally and analytically investigates the length scaling for the boundary layer separation induced by two incident shock waves in a Mach 2.73 flow. The experimental results show that the separation point moves downstream with increasing shock wave distance. For the dual-incident shock wave-turbulent boundary layer interactions exhibiting a coupling separation state, the upstream interaction length approximately linearly decreases with increasing distance, and the decrease rate increases with the second deflection angle. A prediction method for the upstream interaction length is proposed, with a relative error of about 10% compared to the experimental result.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Xin Li, Yue Zhang, Huijun Tan, Yi Jin, Chao Li
Summary: This study investigates the interactions between the boundary layer and two successive incident shock waves in supersonic mixed-compression inlets. Experimental and analytical methods are used to study the turbulent boundary layer separation induced by single and dual shock waves. The study reveals different flow features and separation region shapes depending on the distance between the shock waves.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Matthew Bross, Sven Scharnowski, Christian J. Kaehler
Summary: Studies have shown that in compressible turbulent boundary layer flows, the frequencies of superstructures have slightly longer streamwise wavelengths, and there is a distinct increase in the spanwise spacing of superstructures in supersonic cases compared to subsonic and transonic turbulent boundary layers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Shibin Cao, Jiaao Hao, Peixu Guo, Chih-Yung Wen, Igor Klioutchnikov
Summary: This work investigates the stability of hypersonic flow over a curved compression ramp using stability analysis tools and direct numerical simulations. The study considers the effects of corner rounding on the separation bubble flow to suppress the intrinsic instability of the compression-ramp flow. Global stability analysis and resolvent analysis are employed to analyze the intrinsic instability and response of stable flows to external disturbances. The results show that low-frequency streamwise streaks with a specific spanwise wavelength are strongly amplified in the considered flows, and the separation bubble has little influence on the selection of the spanwise wavelength of streamwise streaks.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Shibin Cao, Jiaao Hao, Igor Klioutchnikov, Chih-Yung Wen, Herbert Olivier, Karl Alexander Heufer
Summary: This work investigates the transition process in a hypersonic flow over a cold-wall compression ramp through direct numerical simulation (DNS) and global stability analysis (GSA). The study finds that the intrinsic instability of the flow system triggers the formation of streamwise counter-rotating vortices and boundary-layer streaks, which have a significant influence on the transition process.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Eric Won Keun Chang, Wilson Y. K. Chan, Timothy J. McIntyre, Ananthanarayanan Veeraragavan
Summary: In this study, experimental investigations were conducted on hot-wall hypersonic impinging shock interactions in a flight-representative environment. The results showed that with higher wall temperatures and lower unit Reynolds numbers, flow separation size increased. The data did not align well with existing separation correlations due to the stronger shock strength, and instead followed a scaling law based on pressure ratio and wall temperature ratio.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Longsheng Xue, Yun Jiao, Chengpeng Wang, Keming Cheng
Summary: This study investigates the impact of impinging shock angle on separation configuration and pressure distribution, proposing a theoretical equation for predicting pressure plateau based on minimum entropy production. Experimental validation and theoretical analysis reveal impinging shock strength as a main factor in predicting pressure plateau.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Nan Li, Juntao Chang, Kejing Xu, Daren Yu, Wen Bao
Summary: The study investigated the unstable behavior of a shock train system in a back pressured duct with incident shocks. It found that as the shock train enters the SWBLI region, divergent vibration emerges, leading to instability. An analysis based on the feedback mechanism identified a criterion for this instability.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Shibin Cao, Jiaao Hao, Igor Klioutchnikov, Herbert Olivier, Karl Alexander Heufer, Chih-Yung Wen
Summary: This study investigates the flow characteristics of hypersonic flows over compression ramps with different leading-edge radii using numerical simulations and global stability analysis. The results show that increasing the leading-edge radius can suppress flow separation, reduce aerodynamic heating, and stabilize the flow system.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Peng-Jun-Yi Zhang, Zhen-Hua Wan, Si-Wei Dong, Nan-Sheng Liu, De-Jun Sun, Xi-Yun Lu
Summary: This study presents a comprehensive analysis on the extreme events in compressible turbulent boundary layers using direct numerical simulations. The study focuses on the relationship between the extreme events and wall streaks as well as alternating positive and negative structures. A novel decomposition method is proposed to quantify the momentum and energy transport mechanisms.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
David J. Lusher, Neil D. Sandham
FLOW TURBULENCE AND COMBUSTION
(2020)
Article
Computer Science, Interdisciplinary Applications
Arash Hamzehloo, David J. Lusher, Sylvain Laizet, Neil D. Sandham
Summary: The study aims to quantify the potential of the new TENO schemes in fully turbulent supersonic flow. Results show that the TENO schemes exhibit significant performance improvements over the WENO schemes in resolving turbulent structures, especially in terms of statistical accuracy and three-dimensional vortical structure resolution.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS
(2021)
Article
Mechanics
David J. Lusher, Neil D. Sandham
JOURNAL OF FLUID MECHANICS
(2020)
Article
Mechanics
Adriano Cerminara, Neil Sandham
JOURNAL OF FLUID MECHANICS
(2020)
Article
Thermodynamics
F. Alves Portela, N. D. Sandham
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2020)
Article
Engineering, Aerospace
Adriano Cerminara, Tobias Hermann, Hassan Saad Ifti, Ralf Deiterding, Neil Sandham, Matthew McGilvray
Summary: This study investigates the effects of boundary layer instabilities and transition on wall cooling performance in a Mach 5 low-enthalpy flow over a flat plate through a combined numerical-experimental approach. Results show that unstable boundary layer modes significantly affect the wall cooling performance, with different amplitudes leading to different states of the boundary layer impacting the heat flux to the wall.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Engineering, Aerospace
Julien Lefieux, Eric Garnier, Jean-Philippe Brazier, Neil D. Sandham, Antoine Durant
Summary: In hypersonic flows, numerical simulations and experimental validation were conducted to study roughness-induced transition mechanisms on a wedgelike forebody at Mach 6. The linear stability analysis accurately predicted flow instability characteristics and showed good agreement with experiments. Unsteady simulations in trip array configurations revealed higher frequencies of the most unstable secondary instabilities, without changing the transition mechanisms.
Article
Physics, Fluids & Plasmas
F. Alves Portela, A. Busse, N. D. Sandham
Summary: The study found that, except for low-pass filtered surfaces, the roughness function remains relatively constant, while the pressure counterpart is largest for high-pass filtered surfaces. Existing correlations can only explain qualitative effects and would benefit from introducing additional parameters. The influence of the roughness wave-number spectrum on turbulence diminishes within the roughness layer.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Physics, Fluids & Plasmas
Arash Hamzehloo, David J. Lusher, Sylvain Laizet, Neil D. Sandham
Summary: Counter-flow configurations are known for their high efficiency mixers due to the high turbulence intensities, and this paper introduces a simplified version of the problem suitable for direct numerical simulation. The turbulent flow problem between two walls shows distinct characteristics compared to conventional channel flows, with inflectional mean flow and significantly higher turbulence intensity. The study also reveals the potential use of this configuration to investigate compressibility effects on turbulence when certain conditions are met.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Computer Science, Interdisciplinary Applications
David J. Lusher, Satya P. Jammy, Neil D. Sandham
Summary: OpenSBLI is an open-source code-generation system for compressible fluid dynamics, written in Python, with support for high-order finite difference solving and shock-capturing. It generates a complete CFD solver in a domain specific language, OPS, enabling large-scale parallel execution on various computing architectures. The system demonstrates good weak and strong scaling on multi-GPU clusters, showcasing the efficiency of code-generation and domain specific languages for complex fluid flow simulations on emerging computing architectures.
COMPUTER PHYSICS COMMUNICATIONS
(2021)
Article
Mechanics
Pradeep Moise, Markus Zauner, Neil D. Sandham
Summary: This study investigates the effect of flow parameters on transonic buffet and reveals that the physical mechanisms underlying laminar and turbulent buffet are the same. Additionally, it demonstrates the occurrence of Type I buffet on a supercritical aerofoil.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Thermodynamics
Markus Zauner, Pradeep Moise, Neil D. Sandham
Summary: This study investigates the flow physics of transonic buffet using scale-resolving simulations with span-periodic boundary conditions. It reveals the coexistence of multiple modes of flow unsteadiness over an unswept laminar-flow wing section, including a low-frequency transonic buffet mode, an intermediate-frequency separation bubble mode, and high-frequency wake modes associated with vortex shedding. The findings show that the intermediate frequency mode is more sensitive to Reynolds-number effects compared to Mach number, which is the opposite trend to transonic buffet. Spectral proper orthogonal decomposition is used to analyze the spatial structure of these modes.
FLOW TURBULENCE AND COMBUSTION
(2023)
Article
Engineering, Aerospace
Pushpender K. Sharma, Ralf Deiterding, Adriano Cerminara, Neil Sandham
Summary: The study investigates the transpiration-based cooling method for high-speed vehicles and examines the effects of transition location on the cooling performance. Results show that the cooling effectiveness is strongly dependent on the transition location.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)
Article
Mechanics
Alexander Gillespie, Neil D. Sandham
Summary: This study investigates the effect of sidewall confinement on supersonic channel and square duct flows with and without shock trains through numerical simulations. Comparable secondary flow vortices are observed in both cases. The absence of a separation region at the leading shock in the duct case results in lower flow deflection and reduced shock strength compared to the channel case. The sidewalls cause a longer shock train with a larger number of shocks. A modified model based on a momentum thickness-based blockage parameter improves the consistency between the channel and duct cases.
Article
Thermodynamics
Arash Hamzehloo, David J. Lusher, Neil D. Sandham
Summary: Counter-flow configurations provide an efficient framework for studying high intensity turbulent mixing processes. The direct numerical simulations in this study show that compressibility has direct effects on density dilatation and indirect effects on Favre normal stresses.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2023)
