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В.Б. Сапожников, Н.И. Авраамов
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Инженерный журнал: наука и инновации
# 2·2017
Conditions for gas cavity collapse in fluid during
the transition from weightlessness to short-term
exposure to individual G-force pulses
©V.B. Sapozhnikov, N.I. Avraamov
BaumanMoscowState Technical University, 105005, Moscow, Russia
We present experimental investigation results for the gas cavity collapse processes in
propellant tanks of liquid propellant rocket propulsion plants under free (nonperturbed)
orbital (suborbital) flight conditions, subjected to short-term individual g-force pulses.
We defined the structure of dimensionless groups that link the maximum cavity volume to
the amplitude and duration of a g-force pulse and to the physical properties of the fluid,
so that the cavity does not collapse under the influence of the buoyant force when floating
up. We carried out our experimental investigation using a weightlessness bench imple-
menting reduced gravity conditions during free fall of the equipment being tested, and
employing a flying laboratory moving along a Keplerian parabola. Results of the experi-
mental studies mean that the nature of the collapse process in the case of free gas cavities
subjected to individual g-force pulses is determined by the dimensionless pulse duration
value and by the surface tension to viscosity ratio. Short-term g-force pulses make it pos-
sible to disregard the effect of viscosity upon the gas cavity collapse process. The cavity
collapse, if it takes place, happens when the pulse duration is over, and is caused by fluid
motion in the bottom hemisphere of the cavity. When the g-force pulse duration is signifi-
cant, the pulse-induced cavity motion in the fluid becomes quasi-stationary, and the free
surface stability is determined by the mass-force field intensity, the capillary viscosity ra-
dius parameter being fixed.
Keywords:
liquid propellant rocket propulsion plant, propellant tank, weightlessness,
g-force, gas cavity, strain, collapse, experimental studies
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