Speaker
Description
Reentry into Earth’s atmosphere and entry into the Martian atmosphere can yield to significant radiative heat loads experienced by the flight configurations. For an Earth-atmosphere, the gas is normally considered optically transparent, but very high temperatures behind the shock will radiate, especially in thermodynamic non-equilibrium conditions. CO2 is the main constituent of the Mars atmosphere and a complex molecule. This molecule and its dissociative products have the ability to strongly emit and absorb radiative heat loads. In fact, previous investigations [1] revealed radiative heating to be crucial not only for the stagnation point region but also from the wake flow. The shock layer is optically denser compared to a shock layer produced by an earth entry. Therefore, a precise radiative transport computation is necessary to capture the extreme gradients of radiative heat loads in the shock layer.
In [2] early results for the reentry of the Fire II flight experiment in air are discussed. Use was made of the k-correlation method, and the results were validated against the flight measurement and different numerical results. [3] applied a further development of this method for Martian flows. In [1] Navier-Stokes fluid flow computations for the 2D axisymmetric test case TC3 are presented. Here, thermal equilibrium and a mixture of perfect gases were assumed. They use a Photon Monte Carlo Method for radiative transport computation initially developed for turbulent sooty flames. The solver was modified to feature not only a correlated-k but also a statistical narrow band model. They found significant radiative heat loads at the rear part of the entry vehicle mostly due to CO2 infrared radiation. Similar results were obtained in [4] by using a axisymmetric Navier-Stokes non-equilibrium flow computations together with a radiative transport ray-tracing discrete ordinates method.
For this investigation, an efficient Euler-Boundary-Layer method [5, 6] for entry flow computations is used. It features equilibrium and chemical non-equilibrium computations for earth atmosphere and equilibrium computations for a Martian atmosphere. The latest development is the inclusion of a two-temperature model to cover vibrational non-equilibrium in air. Within the last couple of years a Photon Monte Carlo Method called StaRad (Statistical Radiation) is developed and implemented. [7, 8]. In our early investigations we focused on detailed comparisons with analytical methods. Here, we could demonstrate its general capabilities and its computational precision. Recently an investigation about full 3D radiative transport computations of entry shock layers in earth atmosphere [8] was presented. Here, a detailed description of the method and a discussion about advantages and disadvantages from variations of the method is given.
Since the StaRad radiative transport solver can be coupled to many spectral modeling methods and databases such as PARADE, NEQAIR or HITRAN/HITEMP with this investigation aims at applying our computational setup to the Erath and Martian atmosphere entry shock layers. Furthermore, a discussion of other variations of the method for a further development of the general Photon Monte Carlo Method will be given.
Since a very efficient fluid flow computation method and a radiation method of arbitrary accuracy and computational time (exact for the fictitious number of infinite bundles) is used, several computations along an entry trajectory will be performed to gain an insight of the total heat loads along the trajectory accounting for radiation. The frequency possibilities will be discussed.
REFERENCES
[1] O. Rouzaud, L. Tesse, T. Soubrie, A. Soufiani, P. Riviere. D. Zeitoun: Influence of radiative heating on a Martian orbiter, J. Thermophys. Heat Transf. 22 (2008), pp. 10-19.
[2] Ch. Mundt, J. Garcia-Garrido, F. Goebel: Implementation of gas radiation models in the CFD code NSMB for the analysis of high enthalpy flows of re-entry problems, 6th International Workshop on Radiation of High Temperature Gases in Atmospheric Entry, 24-28 November 2014, St. Andrews, UK.
[3] J. Garcia, A. Pudsey, Ch. Mundt: Numerical simulations of radiative heat effects in a plasma wind-tunnel flow under Mars entry conditions, Acta Astronautica, vol. 11, pp. 334-341, 2018.
[4] N. Bédon. M. Druguet, P. Boubert; Modelling of radiative fluxes to the heat shield of a Martian orbiter, Int. J. Aerodyn 4 (2014), pp. 154-157.
[5] F. Monnoyer, Ch. Mundt, M. Pfitzner: Calculation of the hypersonic viscous flow past reentry vehicles with an Euler-boundary layer coupling method, AIAA-paper 90-417, 1990.
[6] Ch. Mundt: Calculation of hypersonic, viscous non-equilibrium flows around reentry bodies using a coupled Euler/boundary layer method, AIAA-paper 92-2856, 1992.
[7] J. Bonin, Ch. Mundt: 3d Monte Carlo radiative transport computation for Martian atmospheric entry, 8th Int. workshop on Radiation of high temperature gases for space missions, Madrid, 2019.
[8] J. Bonin, Ch. Mundt: Full 3D Monte Carlo radiative transport for hypersonic entry vehicles,
doi.org/10.2514/1.A34179, 2018 and AIAA Journ. Spacecraft & Rockets, vol. 56, pp. 44-52, 2019.
Summary
Since a very efficient fluid flow computation method and a radiation method of arbitrary accuracy and computational time (exact for the fictitious number of infinite bundles) is used, several computations along an entry trajectory will be performed to gain an insight of the total heat loads along the trajectory accounting for radiation. The frequency possibilities will be discussed.
