Instabilities of thermocapillary convection in a half-zone at intermediatePrandtl numbers

The stability of thermocapillary convection inside a cylindrical liquid bri dge is studied using both a direct numerical simulation of the three-dimens ional problem and linear stability analysis of the axisymmetric basic state . Previously this has been studied extensively for low and high Prandtl num bers. However, the intermediate range of Prandtl numbers between approximat ely 0.07 and 0.8 which joins the low and high ranges is quite complicated a nd has not been studied to the same extent. One striking feature is that th e axisymmetric base state is much more stable in this intermediate range th an at high or low Prandtl numbers. We identify four different oscillatory m odes in this range, which have different qualitative features. Direct numer ical simulations have been carried out for representative parameter values, and show that the bifurcations are supercritical. (C) 2001 American Instit ute of Physics.