Microstructure and gas–surface interaction of a carbon/carbon composite in atmospheric entry plasmas

The surface roughness features that develop on a three-dimensional (3D) carbon/carbon (C/C) composite during ablation, that is, material loss and morphology distribution on the wall, were investigated, and a microstructure model was established to analyze the flow field characteristics on the C/C composite surface. The model relies on two changes of scale: (i) the multi-wave height (bundle) varies from 50 μm to 110 μm and (ii) the bundle diameter varies from 0.3 mm to 0.5 mm. At each scale, the 2D full Navier–Stokes surface equation was solved numerically to obtain the heat, friction, and pressure in the steady state. Roughness disturbs the flow properties of the boundary layer, creating additional heat flow and aggravating ablation. Numerical results in a hypersonic gas-thermal environment show the distribution characteristics of the coarse-walled heat flow. Thermochemical ablation preserves the roughness profile and wavefront, which changes the distribution of the external flow field. The flow-heat-ablation analogy study can effectively characterize the flow-field distribution characteristics and timely heat and mass transfer responses of materials under rough walls. Innovative microstructure simulation showcases the intrinsic relationship between microstructure roughness, ablativity, and thermal mechanical properties. These intrinsic laws and data can make significant contributions to the design and optimization of thermal protection systems.