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Gurunath Gandikota

Instabilities of fluid interfaces in microgravity under sudden or periodic change of acceleration

Published on 16 December 2013
Thesis presented December 16, 2013

The behavior of a near-critical fluid subjected to vibration or a rapid variation of acceleration is an extremely interesting topic of research. The resulting physical phenomena are of great interest in view of the fundamental physics involved and have great relevance to the space industry. The thesis addresses mainly three problems: (i) study of the interaction of harmonic vibration with a thermal boundary layer of a supercritical fluid under the absence of gravity, (ii) study of the interaction of vibration with the liquid−vapor interface of a near−critical fluid under various gravity levels (Faraday and frozen wave instabilities, dynamic equilibrium of the interface) (iii) study of the geysering phenomenon inside a reservoir partially filled with a liquid when it is subjected to a rapid variation of gravity. Experiments are conducted onboard the zero−g installations HYLDE and OLGA developed by CEA Grenoble using H2 and O2 as the working fluids. Numerical simulations are carried out using finite volume codes based on SIMPLER (for the problem involving the supercritical fluid) and VOF−PLIC (for the interface dynamics problem under rapid variation of gravity). New and interesting results have been obtained. Various phenomena like the Faraday instability and the frozen wave instability in the sub−critical region and the parametric instability and the Rayleigh−vibrational instability in the supercritical region have been quantified. The experiments have successfully explained the reason behind the transition of the Faraday instability into vertical band pattern very close to the critical point. Experiments and numerical simulation of the geysering phenomenon have helped to evolve empirical correlations for the bubble rise and geyser edge velocities taking into account the effect of walls on these velocities.

Hydronynamic instabilities, Lowgravity, Cryogenic fluids, Space

On-line thesis.