Quasi Steady State Effect of Micro Vibration from Two Space Vehicles on Mixture During Thermodiffusion Experiment

Abstract

The numerical simulations of a thermodiffusion experiment in atmo- spheric pressure binary mixtures of water and isopropanol subject to micro-vibrations at reduced gravity are presented. The vibrations are induced on board ISS and FOTON-M3 due to many different reasons like crew activity, spacecraft docking or operating other experiments, etc. The effects of micro-gravity vibration were inves- tigated in detail on all of the mixture properties. The influences of different cavity sizes as well as different signs of Soret coefficients in the solvent were considered. In this paper, the thermodiffusion experiment was subjected to two different g-jitter vibrations on board ISS and FOTON-M3 as a cavity with a lateral thermal gradi- ent, filled with a mixture of water and isopropanol, is numerically simulated. The full steady-state Navier-Stokes equations, as well as the energy, mass transport and continuity equations were solved numerically using the finite element method. It must be noted that two different methods to present micro gravity vibrational ac- celeration on ISS and FOTON-M3 were performed and programmed in MATLAB to find proper value of acceleration at any step time. All physical properties includ- ing density, mass diffusion and thermodiffusion coefficients were assumed variable as function of temperature and concentration using PC-SAFT equation of state. Assuming all physical properties to be variable made the results more practical in comparison with the constant model, particularly in the ISS cases. The separation behavior of isopropanol and water in terms of the concentration profiles as well as the thermodiffusion coefficients was in agreement with the experimental trends with a small discrepancy for FOTON cases; however, the ISS results show a strong single convection cell that disturbed the pure diffusion process.