The effects of a range of solid/liquid conductivity ratios on convection and flow during solidification of pure gallium in an inverted Bridgman apparatus have been investigated. A variety of steady and unsteady flow patterns, both symmetric and asymmetric, were observed and compared to available spectral results. Transition Rayleigh number values have been identified. The effects of anisotropy in thermal conductivity of gallium on the flow patterns were included. The computational method based on a fixed grid enthalpy formulation has been extended to model convection and anisotropic conduction during directional solidification. (C) 2004 Elsevier Ltd. All rights reserved.