Porous media find their wide applications in the aerospace industry, as effective ways for noise reduction or passive flow controls. Extensive numerical and experimental studies have been conducted to understand their effect on the overlying grazing flow, which stays laminar in most of the time. Only a few work have focused on the fully turbulent flows over such type of materials, with the flow speed limited in the low subsonic regime. The objective of this work is to fill in the gap of the study about high-speed (supersonic) turbulent flows, by performing high-fidelity numerical simulations of channel flow turbulence over an acoustically permeable wall. It is also of interest to understand the interaction between porous surfaces and high-speed turbulence, which could inform possible flow control design efforts for hypersonic turbulence.

COMING SOON!

The heat transfer and shear stress in objects moving at hypersonic speeds are significantly affected by the laminar to turbulent boundary layer transition. The durability and optimization of vehicles with this purpose, therefore, is closely connected to transition delay. Techniques traditionally used to control the boundary layer in low speed flows are not scalable to high speeds due to the harsh environmental conditions. Ultrasonically absorbing coatings (UAC) have shown a great potential in delaying transition and integration with hypersonic vehicles. Their development, though, depends currently on the realization of experiments with hypersonic flows, which are also a technological barrier. The objective of this work is to reproduce the absorption of an UAC, through an impedance boundary condition (IBC), of artificially introduced acoustic modes in a high speed flow simulation over a cone.

The time domain impedance boundary condition (TDIBC) method was used by Sousa et al (JSR, 2018) to model the attenuation of unstable perturbations in a hypersonic boundary layer. The impedance curve introduced at the surface was informed by low-order models and benchtest experiments of Carbon-matrix/Carbon-fiber (C/C) porous material. The result of the multipole fit at three different boundary layer edge pressures (p_e) is collected hereafter in a compressed folder. The folder collects the data and a python script used to reconstruct the impedance (Z_*) as well as wall softness (S) curves as a function of frequency.

The objective of this work is to model the linear, nonlinear and saturation regimes of transition and understand their energy sources through direct numerical simulations (DNS) and nonlinear parabolized stability equations (NPSE) of spectral broadening of second mode waves over a hypersonic flared cone designed to maintain a constant thickness boundary layer throughout its length. Although dynamics in the linear regime are well understood, they will be used as the starting point to unsderstand the influence of nonlinearities in the flow. A flared cone offers the perfect test bed for this fundamental study as it enhances the disturbance spatial growth.