Speaker
Description
The current study is aimed at developing a simulation framework that is rooted in ab-initio theory and deals with thermal, chemical, and radiative non-equilibrium during hypersonic planetary entry in a unified manner. Computing the population of individual energy states or the radiative intensity corresponding to a given frequency is unfeasible, even for the simplest flow problem, owing to the large number of internal levels and possible collisional/radiative excitation pathways in a gas. The prohibitive cost of state-to-state kinetics is remedied in the present work by adopting a reduced-order model based on coarse graining and the maximum entropy principle [1]. Additionally, an adaptive grouping methodology [2] to identify and lump together groups of states that are likely to equilibrate faster with respect to each other is employed which results in more accurate reduced-order models.
The problem of model-reduction for radiation transfer problems is motivated by a desire to accurately characterize the rapid variation in spectral properties such as opacity and emission using averaged or “homogenized” frequency-independent values. The use of multi-group Planck-averaging in conjunction with a novel binning strategy allows this complex behavior to be modeled in a cost-effective manner. The present work also employs a finite-volume (FV) approach to compute the angular-integrated three-dimensional radiative intensity for the entire domain which opens the door to flow-radiation coupled calculations [3].
The new physics-based modeling framework is used to analyze the flowfield and radiative heat transfer in the backshell of the Mars Science Laboratory (MSL) entry vehicle during hypersonic planetary entry. The coarse-grain model allows a high-fidelity (non-Boltzmann) description of the CO2 vibrational state population. The reduced-order radiative transfer equations solved using the FV approach enable accurate computationally-efficient coupled calculations of the radiative heat flux emanating from the major CO2 infrared bands.
REFFERENCES
1. Y. Liu, M. Panesi, A. Sahai, and M. Vinokur, J. Chem. Phys., 142, 134109, 2015.
2. A. Sahai, B. Lopez, C.O. Johnston, and M. Panesi, J. Chem. Phys., 147, 054107, 2017.
3. A. Wray, ICCFD7, 1003, 2012.
Summary
This work presents a unified, computationally tractable, physics-based modeling framework for analyzing the flowfield and radiative heat transfer in the backshell of the Mars Science Laboratory (MSL) entry vehicle during hypersonic planetary entry.
