Interactions between the near-wall turbulent structures and heavy particles in compressible turbulent boundary layers

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.