Thermal striations on the free surface of a liquid bridge

Stability of thermoconvective flows in liquid bridge for Pr=107.8 is numerically investigated under terrestrial conditions. The heat transfer through the interface plays an important role at the onset and development of oscillatory flows. In the case of linear temperature distribution in the ambient gas the instability begins as hydrothermal wave at Re1cr=112. A new, high frequency instability, is found in the case when the temperature of the gas near interface is uniform. This instability, starting also at Re1cr=112, is not a hydrothermal wave, but an axially running wave, which propagates from hot towards the cold wall in the thin layer of liquid near the interface. Later on, at Re2cr=170, a hydrothermal wave, spreading in the azimuthal direction appears in the system as the result of a second bifurcation.