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Projecte llegit

Títol: CFD study of two-phase flows in microgravity/hypergravity conditions with OpenFOAM


Estudiants que han llegit aquest projecte:


Director/a: ARIAS CALDERÓN, SANTIAGO

Departament: FIS

Títol: CFD study of two-phase flows in microgravity/hypergravity conditions with OpenFOAM

Data inici oferta: 18-07-2018     Data finalització oferta: 18-03-2019



Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
Two-phase, Spatial conditions, Microgravity, Hypergravity, Numerical simulations, CFD, OpenFOAM
 
Descripció del contingut i pla d'activitats:
Fluids behave differently depending on the gravitational
conditions. This behavior is expected to be different, and often
unknown, than in normal terrestrial conditions, both for low
gravity (orbiting satellites, ISS) and hypergravity environments
(re-entry trajectories, planets with larger masses than Earth).
This behavior can be surprising and sometimes dangerous for the
good performances of the onboard subsystems of space vehicles or
even the life support subsystems. The main goal of this TFG is to
study some of these phenomena by means of Computational Fluid
Dynamics (CFD) analyses. OpenFOAM, an open source software, is
the solver used in this study.
 
Overview (resum en anglès):
Nowadays we are in the greatest space and air era ever, in which technology has been forced to develop up to the point of being applied in gravity conditions that cannot be found
on Earth surface. The application of two-phase fluid systems in spacecraft are of great interest to this sector due to its advantages, including: weigh reduction, enhanced performance and efficiency improvement, all of them in comparison with mono-phase fluids. The most remarkable examples where are used biphasic fluids are space bioreactors, chemical gas-liquid contactors, propulsion systems, thermal management systems including fuel
or electronics cooling, and spatial life-support systems. Even though the wide variety of technological applications, there are very few hypergravity studies and most of them focus on making spacecraft’s components the more resistant as possible. Therefore, the fluid flow research in hypergravity conditions is a very unknown area that requires further investigation.
Some years ago Francesc Suñol and Ricard González-Cinca performed an experimental analysis of the effects of gravity on bubble formation and rise in a low viscosity liquid (distilled-water). This study was carried in the hypergravity environment generated by the large diameter centrifuge of the European Space Agency. So, in the work presented it has been reproduced the mentioned research with a CFD software called OpenFOAM with two main objectives: analyse the same aspects regarding the bubble formation and rise processes, since its behaviour changes as the gravity level increases, and compare the results obtained from the numerical simulations with the previous ones, in order to validate the CFD program for this use.
This project has an important part that consists in validations, where we have studied the most important parameters for the simulations, such as: the contact angle of the fluid and the convergence of the mesh and time step. In addition to the analysis of the transient between two consecutive bubbles, and the bubble formation process in normal gravity and in hypergravity conditions. Then, we performed the final tests to study the bubble rise velocity and volume. The corresponding simulations were set in different hypergravity conditions, for three gas injection velocities: 0:03m=s, 0:06m=s and 0:1m=s.
Finally, comparing the OpenFOAM results with the ones obtained in the previous research, it can be stated that CFD software can reproduce a fluid flow experiment successfully.
The detachment of the bubble from the capillary is determined by surface tensions and buoyancy force, although at higher gravity levels this process is accelerated. Posterior bubble rise follows a zig-zag path that is destabilized and accelerated as gravitational effects increase, which leads to a variation in the oscillation amplitude and frequency, as shown in the previous research.


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