Wall temperature effects of compressible turbulent boundary layers at moderate Reynolds numbers Ming Yu, Jiahui Qin, Pengxin Liu, Xianxu Yuan, Chun-Xiao Xu Journal of Fluid Mechanics, 2026 In this paper, we investigate the influences of wall temperature on compressible turbulent boundary layers at free-stream Mach number 6.0 and moderate Reynolds numbers. The findings demonstrate that turbulent statistics, including the logarithmic scaling of Reynolds stresses in the overlap region, the presence of very-large-scale motions in the outer layer, and their superposition on near-wall turbulence, exhibit qualitative invariance across varying wall temperatures. However, the reduced scale separation between near-wall small-scale motions and outer-layer large-scale motions leads to a contraction in the vertical extent of Reynolds stresses adhering to the logarithmic law. Very-large-scale motions are attenuated in viscous units but intensified in global scalings due to the lower free-stream Reynolds number, following approximately the power law. Their superposition effects on near-wall turbulence, when weighted by density, show only weak dependence on wall temperature. Conversely, the modulation of near-wall velocity and temperature fluctuations by very-large-scale motions diminishes with decreasing wall temperature. Through detailed analysis of spanwise spectra in the outer region, a distinct inertial subrange obeying the classical $-5/3$ scaling law is identified, alongside a universal scaling over the dissipative range. These observations suggest that the mechanisms governing energy cascade processes and the associated small-scale turbulent fluctuations remain independent of wall temperature variations.
Translational and rotational motions of inertial prolate particles in compressible turbulent channel flows Yibin Du, Ming Yu, Lihao Zhao, Chongwen Jiang, Xianxu Yuan Physics of Fluids, 2026 This study investigates the dynamics of spherical and prolate spheroidal particles in compressible turbulent channel flows using point-particle direct numerical simulations. We examine particles with a range of Stokes numbers and aspect ratios suspended in compressible turbulent channel flows with bulk Mach numbers from 0.3 to 3.0. Our results show that increased flow compressibility, which introduces non-uniform mean fluid density and viscosity, significantly alters particle spatial distribution, translational and rotational motion, and orientation. At higher Mach numbers, the particle Stokes number under semi-local viscous scaling decreases, leading to a weaker tendency for near-wall accumulation, preferential clustering, and reduced mean slip velocities. Furthermore, a higher bulk Mach number enhances the streamwise alignment of prolate particles at a fixed St+, increases the spinning rate of light particles, and suppresses the tumbling rate of heavy particles. These phenomena are amplified by intensified Lagrangian stretching and streamwise velocity fluctuations, combined with a shorter rotational response time about the particle's major axis. For more elongated particles, the observed increase in mean slip velocity is attributed to a greater probability of streamwise alignment, higher particle mass, and an enhanced spinning tendency.
Spatial development of the secondary flow in a supersonic turbulent square-to-circular transition duct Wenxiao Long, Dapeng Xiong, Ming Yu, Huifeng Chen, Hongbo Wang, Mingbo Sun, Yixin Yang Physics of Fluids, 2026 We conduct direct numerical simulations to study supersonic turbulent flow in a square-to-circular transition duct at Mach 2.7, focusing on the variation of turbulence-driven secondary flows during boundary-layer development. The circumferential pressure gradient induced by cross-sectional shape variation reshapes the distribution of secondary flows, which first move away from the wall and then reattach to it. As the cross-sectional contour gradually approaches a circular shape, the morphology of the secondary flows in the cross section transitions to a circular form. Meanwhile, the cores of the secondary flows continuously migrate away from the corners following a linear law during flow development. Under the development of the secondary flows in the duct, the instantaneous velocity iso-surfaces near the central plane in the square-to-circular transition duct elevate, resulting in a distinct low-speed feature. In the mean flow field, the square-to-circular transition duct exhibits a smaller low-momentum region area in the corner, fuller streamwise velocity profiles and an increased velocity gradient along the corner bisector, which results in higher friction coefficients at the corners compared to the square duct. Additionally, the expansion of the central cross section during the contour transition accelerates boundary-layer growth, resulting in a thicker boundary layer in the transition duct than in the square duct. These analyses provide theoretical insights into the dynamic evolution of secondary flows and the regulation of complex flows within square-to-circular transition duct in the specific flow regime.
Wall attached strucures of velocity and tempreture fluctuations in high-speed turbulent channel flows Junyang LI, Qingqing ZHOU, Dong SUN, Ming YU, Xianxu YUAN, Pengxin LIU, and Wuli Xuebao Acta Physica Sinica, 2025 In this study, a clustering method is used to extract the coherent structures associated with intense streamwise velocity fluctuations and temperature fluctuations in high-speed turbulent channel flow. Based on their spatial locations, these structures are categorized into wall-attached type and wall-detached type. A subset of the wall-attached structures exhibits self-similarity in scale, consistent with Townsend (1976)’s attached eddy hypothesis, and these structures are further classified as squat structure, self-similar structure, and tall structure. Conditional averaging results indicate that the streamwise Reynolds normal stress and the intensity of temperature fluctuations follow a logarithmic law in the logarithmic layer, a phenomenon that aligns with the attached eddy hypothesis; meanwhile, the strong Reynolds analogy relationship between velocity and temperature fluctuations remains valid within these attached structures. Analysis based on the RD (Renard-Deck) identity decomposition reveals that tall structures related to low streamwise momentum mainly control the generation of wall friction and heat flux, while tall structures related to high-temperature events play a main role in the of wall-normal heat flux transfer.
Interactions between the near-wall turbulent structures and heavy particles in compressible turbulent boundary layers Ming Yu, Lihao Zhao, Yibin Du, Xianxu Yuan, Chunxiao Xu Journal of Fluid Mechanics, 2025 In the present study, we investigate the modulation effects of particles on compressible turbulent boundary layers at a Mach number of 6, employing high-fidelity direct numerical simulations based on the Eulerian–Lagrangian point-particle approach. Our findings reveal that the mean and fluctuating velocities in particle-laden flows exhibit similarities to incompressible flows under compressibility transformations and semi-local viscous scaling. With increasing particle mass loading, the reduction in Reynolds shear stress and the increase in particle feedback force constitute competing effects, leading to a non-monotonic variation in skin friction, particularly in turbulence over cold walls. Furthermore, dilatational motions near the wall, manifested as travelling-wave structures, persist under the influence of particles. However, these structures are significantly weakened due to the suppression of solenoidal bursting events and the negative work exerted by the particle feedback force. These findings align with the insight of Yu et al. (J. Fluid. Mech., vol. 984, 2024, A44), who demonstrated that dilatational motions are generated by the vortices associated with intense bursting events, rather than acting as evolving perturbations beneath velocity streaks. The attenuation of travelling-wave structures at higher particle mass loadings also contributes to the reduction in the intensities of wall shear stress and heat flux fluctuations, as well as the probability of extreme events. These results highlight the potential of particle-laden flows to mitigate aerodynamic forces and thermal loads in high-speed vehicles.
Wall shear stress and pressure fluctuations in compressible turbulent boundary layers laden with particles Ming Yu, Yibin Du, Qian Wang, Siwei Dong, Xianxu Yuan Physics of Fluids, 2025 We analyze the direct numerical simulation databases of particle-laden compressible turbulent boundary layers to evaluate the influences of the two-way coupling effects on wall shear stress and pressure fluctuations. Via analysis of one-point statistics, frequency spectra, and instantaneous and conditionally averaged flow fields, we demonstrate that increased particle mass loading progressively suppresses wall shear stress fluctuations associated with high-intensity sweeping and ejecting events. Conversely, fluctuations induced by particle feedback forces intensify but remain insufficient to offset the overall reduction in fluctuation intensity. Pressure fluctuations similarly exhibit reduced intensity at higher mass loadings. Notably, the direct influence of particle feedback forces on wall pressure fluctuations is comparatively negligible, indicating that vortical motions dominate wall pressure fluctuations.
Two-way momentum and thermal coupling particle-laden compressible turbulent boundary layers Ming Yu, Yibin Du, Qian Wang, Siwei Dong, Xianxu Yuan Physical Review Fluids, 2025 This paper employs direct numerical simulations at Mach 2 to reveal how particles with infinite thermal inertia, acting as persistent heat sinks or sources, drastically alter turbulence statistics and coherent structures. Hot particles suppress turbulence by weakening velocity streaks and vortical motions, whereas cold particles amplify Reynolds shear stress and skin friction. Crucially, particle feedback forces inhibit wall-normal fluctuations, with heat transfer aligning coherently with ejection and sweeping events.
A data-driven construction of reduced order model for supersonic boundary layer bypass transition 11th International Symposium on Turbulence and Shear Flow Phenomena Tsfp 2019, 2019
