3 research outputs found
CFD study of two-phase flows in hypergravity conditions with OpenFOAM
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 superfĂcie 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 quĂmics de gas-lĂquid, 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 Ëś 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 lĂquid 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. AixĂ 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 Ă 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 Ă©n 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 enNowadays 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 Sunol and Ricard Gonz ˜ alez-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 [1]
CFD study of two-phase flows in hypergravity conditions with OpenFOAM
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 superfĂcie 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 quĂmics de gas-lĂquid, 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 Ëś 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 lĂquid 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. AixĂ 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 Ă 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 Ă©n 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 enNowadays 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 Sunol and Ricard Gonz ˜ alez-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 [1]
CFD study of two-phase flows in hypergravity conditions with OpenFOAM
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 superfĂcie 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 quĂmics de gas-lĂquid, 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 Ëś 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 lĂquid 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. AixĂ 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 Ă 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 Ă©n 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 enNowadays 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 Sunol and Ricard Gonz ˜ alez-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 [1]