CFD study of the bubble generation process in a T-junction with inversed flows
CovenanteeGuo li Taiwan ke ji da xue
Document typeBachelor thesis
Rights accessOpen Access
Two-phase flow applications are of great interest in the space sector thanks to its advantages, in the recent years, the research on this subject has increased considerably. Some examples can be found in space bioreactors, chemical contactors, life-support systems for human exploration and development of space, etc. Despite the great effort on understanding the behaviour of two-phase flows in microgravity, there are still many unknowns, therefore, further research is needed. In this study, we have dedicated our work to analyse the bubble generation of the water-air combination in a T-junction capillary. The simulations have been performed in a microgravity environment due to the very different behavior when compared to the one observed in the presence of gravitational forces, as well as, despite there is a lot of research in this field, there is still much more to be done. The open source program OpenFoam is used as the main tool for our simulations and Paraview as a post-processing tool. The InterFoam solver is selected to use in order to simulate laminar flow with two incompressible and isothermal phases. The study of numerical simulations has been carried out to compare it with experimental data and therefore, validate the software for this use. Before obtaining the results, convergence tests on the mesh have been performed, in addition to a study to detach the bubbles from the walls, focusing on the contact angle and wettability condition. We validated our mesh and selected the best boundary conditions to perform the finals tests. In the results, we carried out the simulations for three groups of combinations of velocities with U_SL=0.106 m/s, U_SL=0.318 m/s, and U_SL=0.531 m/s and different gas superficial velocity to analyse the behaviour of the bubble frequency, volume, velocity, and longitude. We obtained that simulations and experiments are really similarly qualitatively, with some differences quantitatively. Besides, they adequately reproduced the bubbles formation. By analysing all the parameters, we observe that for lower liquid superficial velocities the simulations approach perfectly to the experiments while increasing its velocity the simulations start having more fluctuations and move away from the experimental data.