Numerical simulations of the dcmix microgravity thermodiffusion experiments to assess the impact of typical international space station reboosting manoeuvres
- Autores: Rafael Jurado Cruz
- Directores de la Tesis: Josefina Gavaldà Martínez (dir. tes.), Jordi Pallarès Curto (codir. tes.), Josep Xavier Ruiz Martí (codir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Henri Bataller (presid.), Alexandre Fabregat Tomàs (secret.), Jeff Porter (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencia, Materiales e Ingeniería Química por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The accurate determination of the thermodiffusion coefficients in ternary liquids systems is relevant because it enables the correct evaluation of transport phenomena. However, on Earth laboratories, the different convective, thermal and concentrational mechanisms, mask its exact determination. For this reason, experiments as the Diffusion Coefficient Measurements in ternary mIXtures (DCMIX) series are conducted in space platforms, where the gravity is reduced. But liquid diffusion and thermodiffusion experiments take a long time because the own nature of the physical processes implied. In space platforms, such as the International Space Station (ISS), the duration of the experiment is a very important variable since it implies a previous global planning in order to make long enough compatible quiescent intervals with the ISS activities. Reboostings to correct the orbit, attitude changes and dockings and berthings to bring astronauts and equipment to the station, produce strong disturbances affecting the quality of the microgravity environment.
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 platform. This analysis has found out that the vibratory limit requirements are not always accomplished, especially during strong disturbances such as reboosting. 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. This thesis provides a new solver implemented in OpenFOAM, for solving thermodiffusion problems in ternary mixtures, with a gravity as a function of time.
During the thermodiffusive step, the closer the reboostings occurs to the moment of measuring the concentration field, the larger the error. 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 diffusive step of the experiment.
