Thermodiffusion of binary fluid mixture in the reduced gravity environment of the international space station

The International Space Station provides a reduced gravity environment to study thermodiffusion. However, the presence of micro-accelerations can induce convection in the fluids that can impede the pure diffusion process. Hence, in order to estimate the accuracy of such diffusion experiments in space, it is important to have a good measure of the impact of such micro-accelerations on the thermodiffusion in the fluid mixtures. Accordingly, in this computational study, the impact of the vibrations on the thermodiffusion process in a binary liquid mixture of water and isopropanol that are at the average temperature and pressure of 300.5 K and 1atm, respectively, have been investigated. In this, computational fluid dynamics tools have been used to simulate the complete set of Navier-Stokes equation coupled with a thermodiffusion model to understand fluid motion in a 2-dimensional rectangular domain. For the simulations, a thermal gradient of 15 K has been employed along the lateral boundaries of the rectangular domain. Further, a vibration of 2 Hz frequency and 56mm amplitude has been imposed as the source terms in the momentum equations. All the physical properties including the molecular and thermal diffusion coefficients have been either assumed variable as function of temperature and concentration using PC-SAFT equation of state or assumed constant. Comparisons have been made between the constant and variable models of the physical properties for the specific Rayleigh vibration along with the ideal zero gravity (0-g) scenarios. It is found that using variable model for physical properties make the results be more realistic in comparison with the constant model.