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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.

This Project, performed in VOLOTEA.S.A Airline, has as main objective to check if FlightKeys 5D, the new program for flight planes, is capable to do the needed computation to perform the flights safetly. The main variables that we will analize are fuel consumption, flight time, flight height respect the meteorological variables (wind, temperature)... The study wants to validate if the flight model builded by FlightKeys respect the values given by the manofacutrer and the real aircraft data. In order to the study, it will be divided by two main stages. The first stage will be a theoretical analisis of the two types of planes that Volotea has, B717 and A319.The methods that we will use will be diferent for the two types of aircraft. For the A319 case, we will use an official simulation program of Airbus called PEP, which will provide us with the needed data to do the theoretical comparation. For the B7171 case, as the it is an old flight we do not hace the software to perform the simulations. We will use the tables that are in the B717 manual. This will cause that the study will be more slowly and less acurate. In the second stage of the research we will do a practic analisis with the real data of the plane. Once we compare this data with the data provide by FlightKeys 5D, we will know if the program give us what it promises to us. Diferent scenarios will be performed in order En ambas etapas y aviones utilizaremos diversos escenarios y así se pretenderá tener un estudio lo más preciso posible. In each phase we will analyse if the provider of FlightKeys 5D accomplish with the specifications that have told us in his program, identifying all the anomalies in order to correct them so the computations of the program can be considered safety for the commercial operation.

Avui en dia ens trobem a l'epoca m ` es important de l'espai i de l'aire, lo qual ha portat a ´ que la tecnologia s'hagi vist obligada a desenvolupar-se fins al punt de poder ser utilitzada en condicions gravitacionals que no es troben a la superfície de la Terra. L'aplicacio de ´ sistemes de fluids bifasics en avions, per ` o sobretot en naus espacials ` es de gran inter ´ es` per al sector a causa dels seus avantatges, entre els quals destaquen: la reduccio de pes, ´ millora del rendiment i millores en l'eficiencia dels sistemes, totes elles en comparaci ` oámb fluids monofasics. Els exemples m ` es notables on s'utilitzen els fluids bif ´ asics s ` on els ´ bioreactors espacials, contactors químics de gas-líquid, sistemes de propulsio, sistemes ´ de gestio t ´ ermica, incloent el refredament de combustible o electr ` onica, i els sistemes de ` suport de vida espacials. Tot i la gran varietat d'aplicacions tecnologiques, hi ha molt pocs èstudis en condicions d'hipergravetat i la majoria d'ells es centren en fabricar components de naus lo mes resistents possible. Per tant, la investigaci ´ o de flux de fluids en condicions ´ d'hipergravetat es una ´ area molt desconeguda que requereix m ` es investigaci ´ o. ´ En Francesc Sunol i en Ricard Gonz ˜ alez-Cinca van realitzar fa uns anys un estudi experi- ´ mental sobre els efectes de la gravetat en la formacio de bombolles i el seu ascens dins ´ d'un líquid de baixa viscositat (aigua destil·lada). Aquest estudi es va dur a terme en l'entorn d'hipergravetat artificial generat per la centrifugadora de gran diametre de l'Ag ` encia ` Espacial Europea. Així doncs, en aquest TFG s'ha reprodu¨ıt l'esmentada investigacioámb un programa CFD anomenat OpenFOAM i amb dos objectius principals: analitzar els mateixos aspectes relatius a la formacio de bombolles i el seu ascens, ja que el seu com- ´ portament canvia a mesura que augmenta el nivell de gravetat, i comparar els resultats obtinguts a partir de les simulacions numeriques amb els resultats de l'experiment previ, ` per tal de validar el programa per aquest us. ´ Aquest projecte te una part important que consisteix en validacions, on hem estudiat els ´ parametres m ` es importants per a les simulacions, com ara: l'angle de contacte del fluid í la convergencia de la malla i del pas de temps. A m ` es de l'an ´ alisi del transitori entre ` dues bombolles consecutives, i el proces de formaci ´ o de bombolles en gravetat normal i én condicions d'hipergravetat. Despres d'aquestes validacions es van realitzar les proves ´ finals per mesurar el volum i la velocitat d'ascens de les bombolles. Les simulacions corresponents es van definir en diferents condicions d'hipergravetat, per a tres velocitats de injeccio de gas: ´ 0,03m/s, 0,06m/s i 0,1m/s. Finalment, comparant els resultats d'OpenFOAM amb els obtinguts de la recerca anterior, es pot afirmar que el programa CFD utilitzat pot reproduir un problema de flux de fluids amb exit. El despreniment de la bombolla del capil ` ·lar esta determinat per les tensions ` superficials i per la forc¸a de flotabilitat, encara que per a valors de gravetat mes alts aquest ´ proces s'accelera. El posterior ascens de la bombolla segueix una traject ´ oria en zig-zag ` que es desestabilitza i accelera a mesura que els efectes gravitacionals s ´ on m ´ es grans, el ´ que comporta una variacio de l'amplitud i la freq ´ u¨encia de l'oscil ` ·lacio, com s'observa en

In the following work an aerodynamic study is explained, which consists in seeing the influence of the earth’s surface on the wind propagation. Specifically in plains, uphill and downhill slopes, basic geometries that represent terrestrial and mountainous areas. Once the wind passes through the mentioned domains, the resulting velocity profile is analysed. All in order to provide scientific evidence to the investigations of wind energy, showing the heights where a wind turbine takes advantage of the maximum kinetic energy of the wind. To make it possible, a free and commercial program in Computational Fluid Dynamics (CFD) called OpenFOAM is used. In it, the physical conditions of the boundaries of each geometry are specified. Like the inlet of the flow, the land through which it spreads, its outlet and the top limitation. The boundary conditions are examined and the most suitable ones for this work are concluded. The roughness is simulated by the ”wall functions”, which represent the obstacle of the terrain. The turbulence that appears in consequence, is analysed by the RANS model, specifically that of k-epsilon. And in order to reduce factors that may increase this turbulence, the inlet velocity that is imposed is reduced. Physical knowledge about the Atmospheric Boundary Layer is taken into account in the work. In addition to having as reference the studies carried out by Richard and Hoxey in 1993, which modelled a theoretical velocity profile adapted to the conditions of the Atmospheric Boundary Layer. Model that is used as the theoretical velocity of each simulation, so the results will be compared with it. Finally, the results obtained are discussed, as well as other factors that are taken into account throughout the work. The study ends with some conclusions about the results and the objective of the proposed research.