Abstract
A two-temperature CFD (computational fluid dynamics) solver is a prerequisite to any spacecraft re-entry numerical study that aims at producing results with a satisfactory level of accuracy within realistic timescales. In this respect, a new two-temperature CFD solver, hy2Foam, has been developed within the framework of the open-source CFD platform OpenFOAM for the prediction of hypersonic reacting flows. This solver makes the distinct juncture between the trans-rotational and multiple vibrational-electronic temperatures. hy2Foam has the capability to model vibrational-translational and vibrational-vibrational energy exchanges in an eleven-species air mixture. It makes use of either the Park TTv model or the coupled vibration-dissociation-vibration (CVDV) model to handle chemistry-vibration coupling and it can simulate flows with or without electronic energy. Verification of the code for various zero-dimensional adiabatic heat baths of progressive complexity has been carried out. hy2Foam has been shown to produce results in good agreement with those given by the CFD code LeMANS (The Michigan Aerothermodynamic Navier-Stokes solver) and previously published data. A comparison is also performed with the open-source DSMC (direct simulation Monte Carlo) code dsmcFoam. It has been demonstrated that the use of the CVDV model and rates derived from Quantum-Kinetic theory promote a satisfactory consistency between the CFD and DSMC chemistry modules.
Highlights
The study of high-speed vehicles re-entering the Earth’s atmosphere is of current interest as witnessed by the ongoing tests on the Orion capsule [1,2]
Despite the significant amount of studies focusing on the subject area since the 1960s [5] a thorough understanding and characterisation of the aerothermodynamic flow conditions during re-entry is yet to be resolved as no definitive models exist to describe the wide range of physical phenomena encountered by the re-entry craft
The newly coded two-temperature solver will be validated considering the contributions of competing mechanisms in isolation and a zero-dimensional adiabatic heat bath will be used for this purpose
Summary
The study of high-speed vehicles re-entering the Earth’s atmosphere is of current interest as witnessed by the ongoing tests on the Orion capsule (see Figure 1a) [1,2]. Mastering the art of the high-speed regime is not solely limited to space missions though and new prospects may emerge such as those related to hypersonic civilian transportation This future vision of air-space transportation is embodied by vehicles, such as the cFASTT-1 [3] shown. The requirements in terms of CFD translate into the need for a solver that makes the distinction between the trans-rotational and the vibrational-electronic temperatures, namely the two-temperature model of Park [8,9] These temperatures are derived from the decomposition of the internal energy into its elementary energy modes. Translational-vibrational and vibrational-vibrational energy exchanges are determined and coupled with an appropriate chemistry module Among such CFD codes dedicated to the hypersonic regime are NASA’s DPLR (Data-Parallel Line Relaxation from the National Aeronautics and Space Administration) [10], LAURA This paper concludes with the prescription of an appropriate combination of chemistry-vibration/chemical rate models for use in a hybrid CFD-DSMC (QK) solver
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