InxGa1-xSb single crystals are to be grown by using a GaSb/InSb/GaSb-sandwich system onboard at the international Space Station (ISS). In order to have a better understanding for the transport phenomena occurring in the melt (solution) of this sandwich system, the dissolution and the growth processes were numerically simulated under a microgravity level of the ISS. Simulations were also performed under the gravitational field of Earth (1g) for comparison. The simulation domain includes the In-Ga-Sb solution (liquid phase) for fluid flow, and heat and mass transfer, and the crucible ampoule (solid phase) for heat transfer. Heat and mass balances were also used at the crystal solution interfaces to examine the dissolution and growth processes globally. Simulation results showed that at 1g, dissolution of the GaSb seed was enhanced clue to the contribution of solutal natural convection, and the solution saturated faster compared with that under microgravity. Diffusion during growth was dominant at the both gravity levels. The GaSb concentration in the solution under microgravity was slightly affected by the temperature distribution in the ampoule. (C) 2013 Elsevier B.V. All rights reserved.