Combined thermocapillary and natural convection in an open square cavity with differentially-heated side walls is studied numerically as well as experimentally. The test fluid is silicone oil with Prandtl number of 105. The shape of fluid-free surface is made either flat or curved to study its effect on the flow. A finite difference scheme to deal with a curved free surface is developed. The experimental results shown agree with the numerical results. With the curved-free surface, the flow and local heat transfer rate are reduced in the corner regions, and a sharp peak in heat transfer rate at the top edge of the cold wall disappears. NomenclatureBo = static Bond number, pgL 2 cr Bo = dynamic Bond number, GrIRcr Gr = Grashof number, gjSATL 3 /*' 2 g = gravitational acceleration h = free surface height L = container dimension Nu = local Nusselt number, Eq. (14) Pr = Prandtl number RO.-surface tension Reynolds number, cr r T = temperature nondimensionalized as (T -T C )/AT T c = cold wall temperature (u, v) = velocity in (;t, y) domain nondimensionalized by v/L (x, y) = coordinate system, (Fig. 1) j8 = volumetric expansion coefficient in Gr AT = temperature difference between hot and cold wall ju, = viscosity v = kinematic viscosity (£, 17) = coordinates, Eq. (1) p = density cr = surface tension o> = temperature coefficient of surface tension T -shear stress at free surface 4> = inclination angle of free surface i f f = stream function 0} = vorticity

An experimental study is made of natural convection oscillations in gallium melts enclosed by right circular cylinders with differentially heated end walls. Cases heated from below are examined for angles of inclination (φ) ranging from 0 deg (vertical) to 75 deg with aspect ratios Ar (height/diameter) of 2, 3, and 4. Temperature measurements are made along the circumference of the cylinder to detect the oscillations, from which the oscillatory flow structures are inferred. The critical Rayleigh numbers and oscillation frequencies are determined. For Ar=3 and φ = 0 deg, 30 deg the supercritical flow structures are discussed in detail.