Results from a numerical modeling study of ZnSe crystal growth by physical vapor transport (PVT) are reported in this paper. The influence of a residual gas is included in the two-dimensional model. The simulations show that the Stefan flux dominates the system and the subtle gravitational effects can be gauged by subtracting this flux from the calculated flow fields. Shear flows, due to solutal buoyancy, of the order of 50 mu m/s for the horizontal growth orientation and 10 mu m/s for the vertical orientation are predicted adjacent to the growing crystal. Whether these flows can fully account for the observed gravity-related growth morphological effects and inhomogeneous solute and dopant distributions is a matter of conjecture. A template for future modeling efforts in this area is suggested which incorporates a mathematical approach to the tracking of the growth front based on energy of formation concepts.