Direct Numerical Simulation of Reacting Turbulent Flow on Ablatable Surface

Abstract

During the atmospheric reentry the probe heatshield suers a significant overheating. The composite materials undergo an ablative process that consumes the heat flux by physico-chemical reactions. The material disappears gradually by sublimation, oxidation. In the case of polycristalline graphite, plasma jet experiments show a structural surface roughness like a scalloped pattern when the flow is turbulent. The main idea of this paper is to characterize the microscale interaction of an ablatable material and a turbulent flow. First, we develop an accurate coordinate transformation from the physical space to curvilinear coordinates in order to ensure the conservation of the high-order scheme and to follow the recession of the ablatable material. This development is implemented in a DNS software that resolves the Navier-Stokes equations in the physical space. Secondly, a study of the turbulent characteristics shows that the roughness (structure and height) depends on the turbulent state. Simulations are performed and confirm the good agreement with plasma jet experimental results.