Influence of surface nanostructures on the catalytic recombination of hyperthermal non-equilibrium flow

Abstract

One of the key challenges for accurate prediction of hypersonic aerodynamic heating is the exothermic uncertainty due to the complex surface catalytic recombination effect, which is caused by the strong interactions between highly non-equilibrium dissociated gas and the thermal protection material surface. Employing engineered surface morphology to improve thermal protection effects has been proposed, but its effects on surface catalytic recombination remain unclear. To address this problem, this work employs the reactive molecular dynamics method to investigate the surface adsorption and recombination characteristics of continuous impingement of atomic oxygen upon eight different nano-structured silica surfaces. A parametric study of the influences of the gas incident angles and the surface structural parameters, i.e., roughness factor and surface fraction, is conducted. The results show that the surface catalytic recombination performance is very sensitive to the incident angle of the incoming gas, and the presence of nanostructures increases the recombination rate. The influence of surface morphology shows a complicated feature, where nanostructures with moderated fin height and high surface fraction are beneficial for the inhibition of surface recombination effects, leading to reduced exothermic heat release. Such microscopic revelation of the surface morphology effect is helpful for accurate prediction of aerodynamic heat and provides guidance for the surface engineering of optimized morphology to achieve improved thermal protection effect.