Passive Oxidation Model and Drag Reduction Mechanism of C/SiC Composites

Utilizing the passive oxidation model of the C/SiC composite, an investigation was conducted into the impacts of fractal dimension, height scale factor, and frequency factor on the morphology of the oxidation interface. The oxide layer and composite layer interface morphologies were simulated using the Weierstrass-Mandelbrot(W-M) function, and the ramifications of varying parameters on interface characteristics were quantitatively analyzed. The findings indicate that the maximum discrepancy in the oxidation interface reconstructed by the proposed model aligns well with experimental measurements. Specifically, the surface fractal dimension and height scale coefficient predominantly influence the feature height, where higher values result in more pronounced interface roughness. Furthermore, the frequency factor exhibits a notable influence on the number of bumps and the generation frequency along the characteristic length direction of the reconstructed interface. Finally, it was proposed to delay the transition of the hypersonic boundary layer by controlling the proportion and distribution of C components in C/SiC composite materials. Numerical simulation results indicate that a wavy oxide layer formed by C/SiC composites with a periodically distributed C component ratio ranging from 0.27 to 1 effectively suppresses the growth of the second mode instability in the boundary layer, thereby reducing both heat and drag.