Natural convection of a liquid metal in circular cylinders locally heated from side wall

An experimental study of oscillatory natural convection in gallium melts enclosed by circular cylinders with locally heated at the mid-height of the cylinder and cooled from the both ends has been done. Numerical analysis has also been performed in a two-dimensional configuration to get information about the steady flow.; The cylinders heated from the mid-height are examined for aspect ratios (Ar = height/diameter) ranging from 2 to 10 and the Rayleigh numbers (based on the half of the cylinder height) ranging from {dollar}2.0times 10sp3{dollar} to {dollar}1.50times 10sp6.{dollar} The temperature fields are measured at six different levels, each having four thermocouples at different azimuthal locations to analyze the thermal convection in the fluid. In the range of Ar larger than 3, the flow is steady axisymmetric when Ra is small. When Ra increases beyond a certain value, the flow becomes non-axisymmetric in the upper half due to a thermal instability. Oscillatory motion appears above a certain Ra in the upper half. When Ar = 2, i.e., smaller than 3, the flow is in toroidal motion before the onset of oscillations. The frequencies and phase relations of the temperature oscillations are investigated in detail.