Numerical analysis on the sublimation of low-temperature ablator models undergoing shape change in a supersonic wind-tunnel

Daniele BIANCHI
2019
Ground testing of ablative materials aims at providing critical data on the material behaviour under relevant conditions for the mission. This is normally done in plasma wind tunnel facilities (i.e., ICP torches, arcjets) although the flow velocity is far from being in the hypersonic regime typical of the actual flight. Hence, in order to perform ablative tests with relevant shape change in a hypersonic facility, non-negligible technical challenges have to be faced. To overcome the limitation
more » ... duced by the reduced total temperature of hypersonic wind tunnels, low-temperature ablators can be used. There is, in fact, a small number of readily available substances that sublimate or ablate in a fashion that can be described fairly accurately by theory at temperatures low enough to make them convenient for use at reasonable supersonic Mach numbers in continuous wind tunnels. Here, a numerical procedure based on CFD analysis to support the definition of the hypersonic capsule shape for the subsequent hypersonic/transonic capsule stability test campaign is presented. The first part of the paper is dedicated to a sensitivity analysis to support the capsule final shape and size selection for experimental testing in VKI facilities. Then, a description of the gas-surface-interaction models implemented into the CFD code for low-temperature ablators thermal response with a discussion of the relevant surface reaction thermodynamics and kinetics is presented. The second part is dedicated to the testing of low-temperature ablators models and their validation including coupled shape-change simulations with mesh evolution and a numerical rebuilding of an experimental test performed in a hypersonic wind tunnel with a camphor model.
doi:10.13009/eucass2019-800 fatcat:nmj5hfravvbxzm4yj74kujuob4