Ming Yu
@tsinghua.org.cn
Department of Aerospace Engineering
Tsinghua University
RESEARCH INTERESTS
Turbulent boundary layer;
Computational Fluid Mechanics
43
Scopus Publications
Scopus Publications
- Wall shear stress and pressure fluctuations in compressible turbulent boundary layers laden with particles
Ming Yu, Yibin Du, Qian Wang, Siwei Dong, and Xianxu Yuan
AIP Publishing
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, and Xianxu Yuan
American Physical Society (APS) - Statistics and dynamics of coherent structures in compressible wall-bounded turbulence
Ming Yu, SiWei Dong, XianXu Yuan, and ChunXiao Xu
Springer Science and Business Media LLC - Modelling aerodynamic forces and torques of spheroid particles in compressible flows
Yibin Du, Ming Yu, Chongwen Jiang, and Xianxu Yuan
Elsevier BV - Momentum and kinetic energy transport in supersonic particle-laden turbulent boundary layers
Ming Yu, Yibin Du, Qian Wang, Siwei Dong, and Xianxu Yuan
American Physical Society (APS)
In the present study, we conduct direct numerical simulations of two-way force-coupled particle-laden compressible turbulent boundary layers at the free-stream Mach number of 2.0 for the purpose of examining the effects of particles on the transport of momentum and kinetic energy. By analyzing turbulent databases with various particle Stokes numbers and mass loadings, we observe that the presence of particles suppresses turbulent fluctuations and can even laminarize flow under high mass loading conditions. This is reflected by the wider and more coherent near-wall velocity streaks, reduced Reynolds stresses, and diminished contributions to skin friction and turbulent kinetic energy production. Additionally, the particle feedback force becomes more dominant in turbulent production near the wall and at small scales as mass loadings increase, which is found to be caused by the residual velocity fluctuations from particles swept down from the outer region. Furthermore, we identify that particle dissipation, resulting from the relative velocity between the fluid and particles, accounts for less than 1% of mean kinetic energy viscous dissipation and less than 10% of turbulent kinetic energy dissipation in the case with the highest mass loading. This suggests a modest impact on the internal energy variation of the fluid if two-way heat coupling is introduced. The elevated mean temperature is found in the near-wall region and is ascribed to the influence of the particle feedback force and reduced turbulent diffusion in high mass loading cases. - Transport of inertial spherical particles in compressible turbulent boundary layers
Ming Yu, Lihao Zhao, Xianxu Yuan, and Chunxiao Xu
Cambridge University Press (CUP)
In the present study, we perform direct numerical simulations of compressible turbulent boundary layers at free stream Mach numbers $2\\unicode{x2013}6$ laden with dilute phase of spherical particles to investigate the Mach number effects on particle transport and dynamics. Most of the phenomena observed and well-recognized for inertia particles in incompressible wall-bounded turbulent flows – such as near-wall preferential accumulation and clustering beneath low-speed streaks, flatter mean velocity profiles, and trend variation of the particle velocity fluctuations – are identified in the compressible turbulent boundary layer as well. However, we find that the compressibility effects are significant for large inertia particles. As the Mach number increases, the near-wall accumulation and the small-scale clustering are alleviated, which is probably caused by the variations of the fluid density and viscosity that are crucial to particle dynamics. This can be affected by the fact that the forces acting on the particles with viscous Stokes number greater than 500 are modulated by the comparatively high particle Mach numbers in the near-wall region. This is also the reason for the abatement of the streamwise particle velocity fluctuation intensities with the Mach numbers. - Hypersonic turbulent boundary layer over the windward side of a lifting body
Siwei Dong, Ming Yu, Fulin Tong, Qian Wang, and Xianxu Yuan
Cambridge University Press (CUP)
In the present study, we performed direct numerical simulations for a hypersonic turbulent boundary layer over the windward side of a lifting body, the HyTRV model, at Mach number $6$ and attack angle 2 $^{\\circ }$ to investigate the global and local turbulent features, and evaluate its difference from canonical turbulent boundary layers. By scrutinizing the instantaneous and averaged flow fields, we found that the transverse curvature on the windward side of the HyTRV model induces the transverse opposing pressure gradients that push the flow on both sides towards the windward symmetry plane, yielding significant effects of the azimuthal inhomogeneity and large-scale cross-stream circulations, moderate and azimuthal independent influences of adverse pressure gradient, and negligible impact of the mean flow three-dimensionality. Further inspecting the local turbulent statistics, we identified that the mean and fluctuating velocity become increasingly similar to the highly decelerated turbulent boundary layers over flat plates in that the mean velocity deficit is enhanced, and the outer layer Reynolds stresses are amplified as it approaches the windward symmetry plane, and prove to be self-similar under the scaling of Wei & Knopp (J. Fluid Mech., vol. 958, 2023, A9) for adverse-pressure-gradient turbulent boundary layers. Conditionally averaged Reynolds stresses based on strong sweeping and ejection events demonstrated that the Kelvin–Helmholtz instability of the strong embedded shear layer induced by the large-scale cross-stream circulations is responsible for the turbulence amplification in the outer layer. The strong Reynolds analogy that relates the mean velocity and temperature was refined to incorporate the non-canonical effects, showing considerable improvements in the accuracy of such a formula. On the other hand, the temperature fluctuations are still transported passively, as indicated by their resemblance to the velocity. The conclusions obtained in the present study provide potentially profitable information for turbulent modelling modification for the accurate predictions of skin friction and wall heat transfer. - On the generation of near-wall dilatational motions in hypersonic turbulent boundary layers
Ming Yu, ZiSong Zhou, SiWei Dong, XianXu Yuan, and ChunXiao Xu
Cambridge University Press (CUP)
Dilatational motions in the shape of travelling wave packets have been identified recently to be dynamically significant in hypersonic turbulent boundary layers. The present study investigates the mechanisms of their generation and their association with the solenoidal motions, especially the well-recognized near-wall self-sustaining process of the regeneration cycle between the velocity streaks and quasi-streamwise vortices. By exploiting the direct numerical simulation databases and orchestrating numerical experiments, we explore systematically the near-wall flow dynamics in the processes of the formation and transient growth of low-speed streaks. We conclude via theoretical ansatz that the nonlinearity related to the parallel density and pressure gradients close to the wall due to the restriction of the isothermal boundary condition is the primary cause of the generation of the dilatational structures at small scales. In fully developed turbulence, the formation and the existence of healthy dilatational travelling wave packets require the participation of the turbulence at scales larger than those of the near-wall regeneration cycles, especially the occurrence of the bursting events that generate vortex clusters. This is proven by the less intensified dilatational motions in the numerical experiments in which the Orr mechanism is alleviated and the vortical structures and turbulent bursts are weakened. - Turbulent kinetic energy transport in high-speed turbulence subject to wall disturbances
Ming Yu, QiLong Guo, ZhiGong Tang, Bo Li, and XianXu Yuan
Elsevier BV - Turbulent heat flux and wall heat transfer in hypersonic turbulent boundary layers with wall disturbances
Ming Yu, Bo Li, QingQing Zhou, Dong Sun, and XianXu Yuan
Elsevier BV - Characterization of very-large-scale motions in supersonic and hypersonic turbulent boundary layers
Ming Yu, SiWei Dong, QiLong Guo, ZhiGong Tang, XianXu Yuan, and ChunXiao Xu
Cambridge University Press (CUP)
Very-large-scale motions are commonly observed in moderate- and high-Reynolds-number wall turbulence, constituting a considerable portion of the Reynolds stress and skin friction. This study aims to investigate the behaviour of these motions in high-speed and high-Reynolds-number turbulent boundary layers at varying Mach numbers. With the aid of high-precision numerical simulations, numerical experiments and theoretical analysis, it is demonstrated that the very-large-scale motions are weakened in high-Mach-number turbulence at the same friction Reynolds numbers, leading to the reduction in turbulent kinetic energy in the outer region. Conversely, the lower wall temperature enhances the very-large-scale motions but shortens the scale separation between the structures in the near-wall and outer regions. - Direct numerical simulation of flow in open rectangular ducts
Ming Yu, Davide Modesti, and Sergio Pirozzoli
Cambridge University Press (CUP)
We study turbulent flow in open channels with a free surface and rectangular cross-section, for various Reynolds numbers and duct aspect ratios. Direct numerical simulations are used to obtain accurate characterization of the secondary motions, which are found to be more intense than in closed ducts, and to scale with the bulk, rather than with the friction velocity. A notable feature of open-duct flows is the presence of a velocity dip, namely the peak velocity is achieved at some depth underneath the free surface. We find that the depth of the velocity peak increases with the Reynolds number, and correspondingly the flow becomes more symmetric with respect to the horizontal midplane. This is also confirmed from the change of the topology of the secondary motions, which exhibit a strong corner circulation at the free-surface/wall corners at low Reynolds number, which, however, weakens at higher $Re$ . The structure of the mean velocity field is such that the log law applies with good approximation in the direction normal to the nearest wall, which allows us to explain why predictive friction formulae based on the hydraulic diameter concept are successful. Additional analysis shows that the secondary motions account for a large fraction of the frictional drag (up to $15$ %). - Influences of wall disturbances on coherent structures in supersonic turbulent boundary layers
Ming Yu, Qingqing Zhou, Hongmin Su, Qilong Guo, and Xianxu Yuan
Springer Science and Business Media LLC - Compressibility effects in supersonic and hypersonic turbulent boundary layers subject to wall disturbances
Ming Yu, QingQing Zhou, SiWei Dong, XianXu Yuan, and ChunXiao Xu
Cambridge University Press (CUP)
In the present study, we investigate the compressibility effects in supersonic and hypersonic turbulent boundary layers under the influence of wall disturbances by exploiting direct numerical simulation databases at Mach numbers up to 6. Such wall disturbances enforce extra Reynolds shear stress on the wall and induce mean streamline curvature in rough wall turbulence that leads to the intensification of turbulent motions in the outer region. The turbulent and fluctuating Mach numbers, the density and the velocity divergence fluctuation intensities suggest that the compressibility effects are enhanced by the increment of the free-stream Mach number and the implementation of the wall disturbances. The differences between the Reynolds and Favre average due to the density fluctuations constitute approximately $9\\,\\%$ of the mean velocity close to the wall and $30\\,\\%$ of the Reynolds stress near the edge of the boundary layer, indicating their non-negligibility in turbulent modelling strategies. The comparatively strong compressive events behaving as eddy shocklets are observed at the free-stream Mach number of $6$ only in the cases with wall disturbances. By further splitting the velocity into the solenoidal and dilatational components with the Helmholtz decomposition, we found that the dilatational motions are organized as travelling wave packets in the wall-parallel planes close to the wall and as forward inclined structures in the form of radiated waves in the vertical planes. Despite their increased magnitudes and higher portion in the Reynolds normal and shear stresses, the dilatational motions show no tendency of contributing significantly to the skin friction and the production of turbulent kinetic energy due to their mitigation by the cross-correlation between the solenoidal and dilatational velocity components. - Wall temperature effects on wall heat flux in high-enthalpy turbulent boundary layers
PengXin Liu, JunYang Li, HongMin Su, Dong Sun, Ming Yu, and XianXu Yuan
Elsevier BV - Coherent structures and turbulent model refinement in oblique shock/hypersonic turbulent boundary layer interactions
Ming Yu, Dong Sun, QingQing Zhou, PengXin Liu, and XianXu Yuan
AIP Publishing
In the present study, we investigate the evolution of turbulent statistics and coherent structures in hypersonic turbulent boundary layers at the Mach number of 5 impinged by oblique shock waves generated by the wedge with the angles of 14°, 10°, and 6°, inducing strong, mild, and incipient flow separation, by exploiting direct numerical simulation databases, for the purpose of revealing the underlying flow physics that are of significance to turbulent modeling. We found that the large-scale structures are amplified within the interaction zone, manifested in the form of large-scale low- and high-speed streaks with the spanwise length scale of boundary layer thickness, and gradually decay downstream, the process of which is extremely long. The abrupt variation in the characteristic length, time, and velocity scales as well as the incompatible viscous dissipation of the mean and turbulent kinetic energy results in the incorrect predictions by the Reynolds-Averaged Navier–Stokes (RANS) equation simulations, provided the models are established based on solving the transport equations of the turbulent kinetic equation and its viscous dissipation (k−ε or k−ω models, for instance). To amend this issue, we propose to refine the parameters in the model as the functions of wall pressure, the flow quantities related to multiple flow features. The RANS simulations with the k−ω SST model utilizing the proposed refinement improve greatly the accuracy of the skin friction, wall heat flux, and Reynolds shear stress downstream of the interaction zone, and the wall pressure distributions in hypersonic turbulence over compression ramp, suggesting its promising prospect in engineering applications. - Predicting near-wall turbulence with minimal flow units in compressible turbulent channel flows
Ming YU, Yalu FU, Zhigong TANG, Xianxu YUAN, and Chunxiao XU
Elsevier BV - Post-shock turbulence recovery in oblique-shock/turbulent boundary layer interaction flows
Ming Yu, SiWei Dong, PengXin Liu, ZhiGong Tang, XianXu Yuan, and ChunXiao Xu
Cambridge University Press (CUP)
The oblique shock impinging on the supersonic turbulent boundary layer leads to a mixing layer and the emergence of large-scale coherent structures within the interaction zone which leave significant velocity defect and turbulence amplification downstream. In the present study, we investigate the turbulence recovery in the post-shock region by exploiting direct numerical simulation data of the oblique-shock/turbulent boundary layer interaction flow at the incoming Mach number of $2.28$ and the shock angle of $33.2^\\circ$ , with special attention paid to the contribution of the mixing layer and large-scale structures to flow dynamics. For that purpose, we propose to split the mean velocity, Reynolds stresses and spanwise spectra into a canonical portion that is constructed according to the statistics of canonical turbulent boundary layers, and a mixing-layer-induced portion. We found that the hidden mixing layer grows with the boundary layer thickness and that the induced mean shear and Reynolds stresses decay at different rates. The mean velocity recovers to the canonical profiles at a distance of 13 boundary layer thicknesses downstream where the mixing-layer-induced mean shear ceases to have strong impacts. The recovery of Reynolds stresses requires 10 boundary layer thicknesses in the near-wall region but a much longer streamwise extent in the outer region due to the slow decay of large-scale motions. These large-scale motions superpose on the near-wall turbulence, intensifying the turbulent fluctuations, yet having a trivial impact on the skin friction, for the contribution of the mixing-layer-induced mean shear and Reynolds shear stress are balanced by the advection term. We further establish a simple physical model capable of approximately predicting the streamwise evolution of mixing-layer-induced mean shear and turbulent kinetic energy. This model suggests that the complete recovery of turbulence in the outer region requires a streamwise extent of approximately 50 boundary layer thicknesses. - Effects of wall disturbances on the statistics of supersonic turbulent boundary layers
Ming Yu, PengXin Liu, ZhiGong Tang, XianXu Yuan, and ChunXiao Xu
AIP Publishing
In the present study, we perform direct numerical simulations to investigate the spatial development and basic flow statistics in the supersonic turbulent boundary layers at the free-stream Mach number of 2.0 over smooth and disturbed walls, the latter of which enforces extra Reynolds shear stress in the streamwise direction to emulate the drag increment and mean streamline curvature effects of rough walls. Such disturbances escalate the growth rate of turbulent boundary layer thickness and the shape factor. It is found that under the rescaled global coordinate, the mean velocity, Reynolds stress, and pressure fluctuation variance manifest outer-layer similarity, whereas the average and fluctuation variances of temperature and density do not share such a property. Compressibility effects are enhanced by the wall disturbances, yet not sufficiently strong to directly impact the turbulent kinetic energy transport under the presently considered flow parameters. The generalized Reynolds analogy that relates the mean velocity and temperature can be satisfied by incorporating the refinement in modifying the generalized recovery coefficient, and that associates the fluctuating velocity and temperature work reasonably well, indicating the passive transport of temperature fluctuations. The dispersive motions are dominant and decay exponentially below the equivalent sand grain roughness height ks, above which the wall disturbances are distorted to form unsteady motions responsible for the intensified density and pressure fluctuations in the free-stream traveling isentropically as the acoustic radiations. - Effects of groove distributions on supersonic turbulent channel flows
YaLu Fu, QingQing Zhou, Ming Yu, HongMin Su, QiLong Guo, and XianXu Yuan
Informa UK Limited - Wall pressure fluctuations in supersonic boundary layers over compression ramps with different turning angles
HengYu Cai, Ming Yu, Dong Sun, ZhengYin Ye, PengXin Liu, and XianXu Yuan
AIP Publishing
In the present study, we investigate influences of shock intensity on wall pressure fluctuations by performing direct numerical simulations of supersonic turbulence boundary layers over compression ramps with different turning angles. We found that as the turning angle increases, low-frequency motions of the separation shock are enhanced, accompanied by enlarged energetic pressure structures with lower convection velocities. By inspecting wavenumber-frequency spectra under the assumption of streamwise homogeneity, we further identified two energetic modes convected at different velocities. The one with the lower convection velocity, namely, the “slow mode,” inherited from the upstream pressure fluctuations of the turbulent boundary layer, is decelerated when passing through the oblique shock, during which the “rapid mode” with pressure fluctuations convected at higher speeds are generated. The increasing turning angle decelerates the slow mode and intensifies the fast mode. The reconstruction of the flow field suggests that the rapid mode is associated with the shear layer generated adjacent to the interaction zone, while the slow mode is associated with the Görtler vortices on the ramp. - A spectral inspection for turbulence amplification in oblique shock wave/turbulent boundary layer interaction
Ming Yu, MingXiang Zhao, ZhiGong Tang, XianXu Yuan, and ChunXiao Xu
Cambridge University Press (CUP)
Turbulence amplification and the large-scale coherent structures in shock wave/turbulent boundary layer interaction flows have been studied at length in previous research, while the direct association between these two flow features is still lacking. In the present study, the transport equation of turbulent kinetic energy spectra is derived and utilized to analyse the scale-by-scale energy budget across the interaction zone, enabling us to reveal the association between the genesis of the large-scale motions and the turbulence amplification. For the presently considered flow with incipient shock-induced separation, we identified in turbulent kinetic energy spectra distribution that the most energetic motions are converted from the near-wall small-scale motions to large-scale motions consisting of velocity streaks and cross-stream circulations as they go through the interaction zone. The amplification of streamwise velocity fluctuation is triggered first, resulting in the emergence of large-scale velocity streaks, which is attributed to the adverse pressure gradient, as indicated by the spectra of the production term. The energy carried by large-scale velocity streaks is transferred to other velocity components by the pressure-strain term, producing large-scale cross-stream circulations. When large-scale motions are convected downstream, their energy is transferred via turbulent cascade to smaller scales and dissipated by viscosity. The spanwise uniform fluctuations, reminiscent of the unsteadiness of the separation bubble, are contributed primarily by the inter-scale energy transfer from the finite spanwise scale motions. - Hybrid numerical method for wall-resolved large-eddy simulations of compressible wall-bounded turbulence
Ming Yu, Yalu Fu, Pengxin Liu, Zhigong Tang, Xianxu Yuan, and Chunxiao Xu
Springer Science and Business Media LLC