Two Phase Flow Solver for Solid Particles in Hypersonic Martian Entry Flows

In the Martian atmosphere heavy storms occur, which transport dust particles even into the higher atmosphere, i.e. up to 40 km of altitude. These particles, with sizes of up to 20μm, consist of silicon oxides and iron oxides may affect the heat load on the heat shield during atmospheric entry. In this present study, these additional loads due to impingement of solid particles in hypersonic entry flows in Martian atmosphere are investigated. The Euler-Lagrangian approach is used for the modeling and simulation of solid particles in hypersonic Martian entry flows. For the simulation, the program SINA (Sequential Iterative Non-equilibrium Algorithm) previously developed at the Institut für Raumfahrtsysteme is used. SINA consists of different solvers that are loosely coupled. The main limitation of the code was that it could simulate only air flows consisting of eleven species. However, taking advantage of the loose coupling between the solvers, the capabilities of SINA are not only extended to simulate gases other than air, but also to two-phase flow applications. For the Martian atmospheric chemistry model, only carbon dioxide (CO2) is taken into account because Mars atmosphere consists of 95.3% CO2. Considering that the entry velocity in the Mars atmosphere is usually around 5-7 km/s, the dissociation of CO2 has to be taken into account. Therefore, a five species model (carbon dioxide (CO2), molecular oxygen (O2), carbon monoxide (CO), oxygen (O) and carbon (C)) is implemented in the code. CO2 has three modes of vibration, because it is a three atomic molecule. Previously in SINA, there was no provision to take into account vibrational energies for the three atomic molecule. Therefore, a vibrational model for the three atomic molecule is developed and implemented in the code. Both phases, the gaseous phase and the particle phase, interact with each other through one-way or two-way coupling. In one-way coupling, there is no influence of the particle phase on gas phase. However, two-way coupling takes into account particle phase impact on the gaseous flowfield. The model for the effect of the flowfield gas on a particle includes drag force and particle heating. An adequate model for the drag force computation is implemented in the model in order to take into account transitional and rarefied flows. The heat transfer model of the particle consists of convective heating and radiation cooling. The radiative heating from the gas to the particle is not taken into account because this model is not available in SINA. Due to relative velocity difference in the gas and particle, the development of the local shock may introduce extra heating to the particle. In order to take into account this effect, a normal stagnation point