Speaker
Description
Entry computations for Martian atmosphere yield to significant radiative heat loads. CO2 is the main constituent of this 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 and accurately predict the heat load on the entry vehicle.
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 [2] 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 [3,4] for entry flow computations is used. It features equilibrium and non-equilibrium computations for earth atmosphere and equilibrium computations for a Martian atmosphere. Within the last couple of years a Photon Monte Carlo Method called StaRad (Statistical Radiation) is developed and implemented. In our early investigations [5,6] we focused on detailed comparisons with analytical methods. Here, we could demonstrate its general capabilities and its computational precision. Recently we published an investigation about full 3D radiative transport computations of entry shock layers in earth atmosphere [7]. Here, a detailed description of the method and a discussion about advantages and disadvantages from variations of the method is given.
Since our Photon Monte Carlo radiative transport solver can be coupled to many spectral modeling methods and databases such as PARADE [8], NEQAIR [9] or HITRAN/HITEMP [10] we move forward with this investigation and apply our computational setup to the Martian atmosphere entry shock layer. 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.
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) 10–19. doi:10.2514/1.28259.
[2] N. Bédon, M. Druguet, P. Boubert, Modelling of radiative fluxes to the heat shield of a Martian orbiter, Int. J. Aerodyn. 4 (2014) 154–174.
[3] C. Mundt, M. Pfitzner, M.A. Schmatz, Calculation of viscous hypersonic flows using a coupled Euler / second oder boundary layer method, Notes Numer. Fluid Mech. 29 (1990) 419–429.
[4] F. Monnoyer, C. Mundt, M. Pfitzner, Calculation of the Hypersonic Viscous Flow Past Reentry Vehicles with an Euler-Boundary Layer Coupling Method, in: 28th Aerosp. Sci. Meet., 1990: pp. 1–10. doi:10.2514/6.1990-417.
[5] J. Bonin, C. Mundt, Validation of Radiative Heat Transfer via Monte Carlo Ray Tracing, in Basic Application, in: 7th Int. Work. Radiat. High Temp. Gases Atmos. Entry, Stuttgart, 2016: pp. 1–4.
[6] J. Bonin, C. Mundt, D. Kliche, Simulations of stagnation point radiative heating rates and spectral analysis of entry vehicles, in: 55th AIAA Aerosp. Sci. Meet. AIAA SciTech Forum, (AIAA 2017-1611), 2017: pp. 1–12. doi:10.2514/6.2017-1611.
[7] J. Bonin, C. Mundt, Full Three-Dimensional Monte Carlo Radiative Transport for Hypersonic Entry Vehicles, J. Spacecr. Rockets. (2018) 1–9. doi:10.2514/1.A34179.
[8] A.J. Smith, A. Wood, J. Dubois, M. Fertig, B. Pfeiffer, L. Marraffa, Plasma Radiation Database PARADE V2.2, 2006.
[9] A.M. Brandis, B.A. Cruden, NEQAIRv14.0 Release Notes, 2014.
[10] L.S. Rothman, I.E. Gordon, Y. Babikov, A. Barbe, D.C. Benner, P.F. Bernath, M. Birk, L. Bizzocchi, V. Boudon, L.R. Brown, A. Campargue, K. Chance, E.A. Cohen, L.H. Coudert, V.M. Devi, B.J. Drouin, A. Fayt, J. Flaud, R.R. Gamache, J.J. Harrison, J. Hartmann, C. Hill, J.T. Hodges, D. Jacquemart, A. Jolly, J. Lamouroux, R.J. Le Roy, G. Li, D.A. Long, O.M. Lyulin, C.J. Mackie, S.T. Massie, S. Mikhailenko, H.S.P. Müller, O. V Naumenko, A. V Nikitin, J. Orphal, V. Perevalov, S. Tashkun, J. Tennyson, G.C. Toon, V.G. Tyuterev, G. Wagner, The HITRAN 2012 molecular spectroscopic database, J. Quant. Spectrosc. Radiat. Transf. 130 (2013) 4–50. doi:10.1016/j.jqsrt.2013.07.002.
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