Transient rising of oxygen bubbles in a fast varying gravity

We report experiments on the transient motion of an oxygen bubble rising in liquid oxygen in a fast varying magneto-gravitational acceleration. In the set-up, a strong magnetic field gradient is applied, which creates in bulk oxygen a body force opposed to its weight. When this gravity compensation is suddenly suppressed, the resulting apparent gravity increases within a fraction of a second from 0 $g_0$ to 0.4 $g_0$ (where $g_0$ is the terrestrial gravitational acceleration). Oxygen bubbles of diameters ranging from 6 mm to 18 mm rise rapidly in the liquid by buoyancy, for values of Galilei and Bond numbers rarely reached with common fluids in terrestrial gravity. The shape of the bubble interface is initially ellipsoidal and evolves toward more complicated shapes during the motion. The time-dependent rising velocity of the bubble is measured during the fast variation of gravity. A comparison of the transient bubble dynamics with classical results obtained in a constant gravity environment enables the time scale of the gravity variation to be precisely quantified.