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Projecte llegit

Títol: Analysis of two-phase flows under microgravity (spatial) conditions using OpenFOAM

Estudiants que han llegit aquest projecte:

Director/a: ARIAS CALDERÓN, SANTIAGO

Departament: FIS

Títol: Analysis of two-phase flows under microgravity (spatial) conditions using OpenFOAM

Data inici oferta: 19-10-2019     Data finalització oferta: 19-05-2020


Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
Microgravity, Two-phase flows, T-junction, Computational Fluid Dynamics (CFD), OpenFOAM
 
Descripció del contingut i pla d'activitats:
Two-phase flows (a mixture of two-fluids, like liquid/liquid or
gas/liquid) are frequently found in all kinds of common on-
ground uses (carbonated beverages, food, cosmetics, etc), but
also in more sophisticated space systems, such as space engines,
bioreactors, thermal systems, life support systems, etc.
Gas/liquid-based systems, lighter than the classical
liquid/liquid systems, suppose an evident economic benefit for
spatial applications. And yet, despite their obvious benefits,
the generation, regulation and control of two-phase flows is not
yet fully understood, and some fundamental questions remain open.

Numerical simulations, or Computational Fluid Dynamics (CFD)
studies, are a very powerful way of approaching the study of two-
phase fluids. CFD allows modifying all the physical parameters
involved in the problem, becoming a more flexible option than
real experiments. In this TFG, the student will work with
OpenFOAM, an open source CFD software of enormous versatility.
 
Overview (resum en anglès):
Two-phase flows have gained importance over the last years due to their multiple and useful applications in space systems. For example, two-phase flows are used in fuel cells micro-channel networks, in the fluid management of Environmental Control and Life Support Systems (ECLSS) or in thermal management systems. However, many problems regarding two-phase flows in microgravity conditions are still open, so further research is needed.

In this study, numerical simulations of gas-liquid two-phase flow are performed in a T-junction capillary. Bubbles are formed as a consequence of the interaction between air and water. The geometry used is the same as in [1, 2, 3] in order to make reliable comparisons with the results extracted from the laboratory experiments performed in the mentioned literature. OpenFOAM is used as the main software for the simulations, and ParaView and MATLAB are used to post-process the data. InterFoam is selected as the solver since it uses an incompressible, immiscible and isothermal Volume of Fluid (VOF) method.

Some validations were made before setting up the definitive cases of the simulations. These validations were related to the adequate capillary length in order to obtain fully-developed flows, to the appropriate mesh quality to get good results and maintain an acceptable computational complexity, to the optimal contact angle value to get close to reality bubble behavior in terms of adherence to the walls, and to the right location of the sampling surfaces responsible for extracting the data. An analysis of the fluid velocity profiles along both of the capillaries of the T-junction was also made.

Bubbles are analyzed in terms of their generating frequency, volume, length and velocity. Bubble volume dispersion is quantified using the polydispersity index. A pressure probe is used to measure the gauge pressure at the very center of the T-junction. Visual comparisons are made between simulation bubbles and experimental bubbles. In the end, the results of the simulations qualitatively fitted the experimental data, validating Computational Fluid Dynamics (CFD) as an alternative and correct tool to perform two-phase flow studies under microgravity conditions.

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