On bubble motion in a rotating liquid under simulated low and zero gravity

Siekmann, J.; Johann, W.

doi:10.1007/bf02482627

Cited by 11 publications

(4 citation statements)

References 5 publications

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“…Second, it is observed in Figure 4.28c that the motion is not centred around the z-axis, which might be due to the residual gravity of about 10 −2 g 0 ∼ 10 −3 g 0 on the three axes. Similar behaviour was reported by Siekmann & Johann (1976), who observed circular paths when rotating a fluid in the presence of residual gravity (10 −2 g 0 ) on one axis. The trajectory of bubbles moving towards the axis of rotation were also measured.…”

Section: Microgravity: Bubble Motionsupporting

confidence: 86%

“…Rosenthal (1962) considered the shape stability of a bubble on the axis of rotation, with the aim of using this method to study the surface tension of the liquid. Siekmann & Johann (1976) analyzed the motion of bubbles under simulated weightlessness in a rotating system, obtaining analytical expressions for their motion. Trajectories and drag forces were studied consequently by Annamalai (1982), Ruggles et al (1988) or Rastello et al (2011).…”

Section: Rotationmentioning

confidence: 99%

“…In order to analyse the decelerating behaviour observed, the forces acting on a bubble inside a rotating fluid in microgravity need to be considered. Siekmann & Johann (1976) carried out an analytical and experimental study (in simulated weightlessness) for a gas bubble migrating in a rotating fluid. The forces acting on the bubble in a rotating fluid on ground are inertia, drag, centrifugal force, gravity and Coriolis force.…”

Section: Spin: Bubble Motionmentioning

confidence: 99%

“…where subscript 0 denotes initial conditions, m l = 4 3 πR 3 ρ l is the mass of the displaced liquid and t is the time. Siekmann & Johann (1976) related K to the Stokes law. However, this law is not applicable in our experiment, since we are in the range of Re > 2 (Kulkarni & Joshi (2005)).…”

Section: Spin: Bubble Motionmentioning

confidence: 99%

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Effects of vibrations applied to fluids at different gravity levels

Garcia Sabaté

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Due to the increasing interest in space exploration, management of two-phase flows in the absence of gravity has become a key aspect in improving the efficiency of technological applications for space missions. Understanding of two-phase flows is essential in the development of future applications and for the improvement of existing ones, not only in microgravity, but also in hypergravity conditions. In this thesis, the effects of external factors such as high and low frequency vibrations, or rotations on two-phase flows are addressed, when these systems are at different gravity levels. A series of experimental setups were developed in order to explore a wide range of phenomena occurring at different gravity levels. The effects of pressure fields on micron-sized particles in the levitation plane of an acoustic field are discussed. Furthermore, an analysis of the motions of two isolated particles is provided and a method to determine the forces between them is presented. The method allows us to experimentally obtain the order of magnitude of the forces, as well as indirectly provide a measurement of the acoustic pressure inside a micro-channel. Two microgravity experiments adapted to a sub-orbital vehicle were designed and built in order to examine the effects of low frequency vibrations and rotation in two-phase flows. This thesis will further analyse the effects observed in bubbles in different liquids. Bubble shape oscillations have been observed at low vibration frequencies, even though bubble dynamics are affected by the walls of the cell. After vibrations were turned off, the aspect ratio of a bubble in high viscosity fluid decays exponentially. Bubble break-up has been observed in the case of lower surface tension and lower viscosity. Focusing on the distribution of the air bubbles during high and low rotation rates, an analysis is presented on the effects on a low surface tension fluid. An investigation is presented on the injection trajectory of bubbles during rotation showing a reasonable agreement with analytical predictions. The detachment and rise of bubbles and bubble trains while an acoustic field is applied in hypergravity conditions are also addressed. Different effects have been observed in this experiment. Focusing on detachment, we provide an expression for estimating the detachment diameter when an acoustic field is applied. In addition, the effect of bubble trains on terminal velocity is discussed. A numerical analysis is also presented and compared to the experimental data. Degut a l'increment en l'interès per l'exploració espacial, la gestió de fluids bifàsics en absència de gravetat ha esdevingut un tema clau per la millora de l'eficiència d'aplicacions tecnològiques per a missions espacials. Arribar a entendre els fluids bifàsics és important per al desenvolupament de futures aplicacions i per la millora de les ja existents, no només en condicions de microgravetat sinó també en condicions d'hipergravetat. En aquesta tesi es tracten els efectes que tenen factors externs com vibracions d'alta i baixa freqüència o rotacions, sobre fluids bifàsics, quan aquests es troben en diferents nivells de gravetat. S'han desenvolupat una sèrie de muntatges experimentals per a explorar els diferents fenòmens que succeeixen a diferents nivells de gravetat. S'analitzen els efectes que tenen els camps de pressió sobre partícules micromètriques en el pla de levitació d'un camp acústic. A més, s'analitza el moviment de dues partícules aïllades i es presenta un mètode per a determinar les forces entre elles. Aquest mètode permet obtenir experimentalment l'ordre de magnitud de les forces, així com obtenir indirectament la mesura de la pressió del camp acústic dins del micro canal. S'han dissenyat i muntat dos experiments de microgravetat adaptats a un vehicle suborbital, per estudiar els efectes de vibracions de baixa freqüència i rotació sobre fluid bifàsics. Es presenta una anàlisi dels efectes observats sobre les bombolles. S'han observat oscil·lacions de forma de les bombolles amb vibracions de baixa freqüència, tot i que la dinàmica es veu afectada per les parets de la cavitat. Després d'aturar la relació d'aspecte d'un fluid d'alta viscositat decreix exponencialment. També s'ha observat trencament de la bombolla, en el cas de baixa tensió superficial i baixa viscositat. Pel que fa a rotació, es fa un anàlisis dels efectes que té sobre un fluid de baixa tensió superficial, centrant-nos en la distribució de bombolles d'aire quan la velocitat de rotació és més alta o més baixa. S'estudia la trajectòria de les bombolles injectades durant la rotació, mostrant concordança amb prediccions analítiques. Per últim, abordem el desenganxament i l'ascens de bombolles i trens de bombolles, mentre apliquem un camp acústic en condicions d'hipergravetat. Durant els experiments s'han observat diferents efectes. Mirant el desenganxament, donem una expressió per estimar el diàmetre de la bombolla quan es desenganxa quan s'està aplicant un camp acústic. A més, es discuteixen els efectes sobre trens de bombolles. També es presenta una anàlisi numèric i es compara amb les dades obtingudes experimentalment.

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Section: Microgravity: Bubble Motionsupporting

confidence: 86%