Numerical simulations of the DCMIX microgravity thermodiffusion experiments to assess the impact of typical International Space Station reboosting manoeuvres

Identifier:  TDX:2941

Handle: https://hdl.handle.net/20.500.11797/TDX2941

Authors:  Jurado Cruz, Rafael

Abstract:
In this thesis, the impact of the ISS reboosting manoeuvres on the DCMIX experiments has been investigated. First of all, the microgravity environment of the ISS has been analysed using the signals recorded by the sensors located in different modulus of the station. This analysis has found out that the vibratory limit requirements are not always accomplished, especially during strong disturbances such as reboostings. These manoeuvres promote the largest level of acceleration onboard the ISS. Therefore, accelerometric signals recorded during reboostings have been used to perform numerical simulations under different reboosting scenarios. A new solver implemented in the open source software OpenFOAM, for solving numerically the different thermodiffusion problems in ternary mixtures, with the gravity as a function of time has also been developed. During the thermodiffusive step of the DCMIX experiments, the closer the reboostings occurs to the moment of measuring the concentration field, the larger the error in the estimation of the Soret coefficients. Also, the method used for quantifying the concentration field can affect the error. The analytical solution can be used in advance, to analyse the sensitivity of the system to the acceleration. The reboosting acting in a direction perpendicular to the temperature gradient has been proven to be the most harmful acting direction, giving an error up to 64% when calculating the diffusion coefficients during the pure diffusive step of the experiment.