High performance modeling of atmospheric re-entry vehicles

Abstract

Re-entry vehicles designed for space exploration are usually equipped with thermal protection systems made of ablative material. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple flow chemistry models. In order to obtain better predictions, an appropriate gas flow chemistry model needs to be included in the CFD calculations. Using a recently developed chemistry model for ablating carbon-phenolic-in-air species, a CFD calculation of the Stardust re-entry at 71 km is presented. The code used for that purpose has been designed to take advantage of the nature of the problem and therefore remains very efficient when a high number of chemical species are involved. The CFD result demonstrates the need for such chemistry model when modeling the flow field around an ablative material. Modeling of the nonequilibrium radiation spectra is also presented, and compared to the experimental data obtained during Stardust re-entry by the Echelle instrument. The predicted emission from the CN lines compares quite well with the experimental results, demonstrating the validity of the current approach.

Numerical Analysis of Surface Chemistry in High-Enthalpy Flows

“…The numerical simulations in this work are conducted using the Navier-Stokes computational fluid dynamics code LeMANS [19], developed at the University of Michigan. It is a general-purpose parallel three-dimensional code that solves the laminar NavierStokes equations, including chemical and thermal nonequilibrium effects on unstructured computational grids.…”

“…(19)] takes into account the nitrogen atom recombination on the wall due to surface catalysis along with the carbon nitridation reaction where the carbon from the surface reacts with the impinging nitrogen atoms. The EleyRideal recombination reaction is used to represent the process of carbon nitridation.…”

“…(18) and, for case 3, it is defined by Eq. (19). The effective reaction efficiency γ for cases 2 and 4 is calculated using Eq.…”

Modeling of Heat Transfer Attenuation by Ablative Gases During the Stardust Reentry

“…The hypersonic aerothermodynamic CFD code used in the present analysis is LeMANS, a finite-volume Navier-Stokes solver [18]. The code assumes that the rotational and translational energy modes of all species can be described by a single temperature T and that the vibrational energy mode and electronic energy mode of all species, as well as the free electron kinetic energy, can be described by another single temperature T ve .…”

Comparison of Transport Properties Models for Flowfield Simulations of Ablative Heat Shields

“…The numerical simulations are performed using the CFD code LeMANS, which was developed at the University of Michigan [6,7]. LeMANS solves the laminar Navier-Stokes equations on unstructured computational grids, including thermochemical nonequilibrium effects with second-order spatial accuracy.…”