The effects of forced ambient velocity on thermal plume behavior in a ceiling vented square enclosure are numerically investigated. Turbulence is modeled by unsteady Favre-averaged Navier-Stokes (UFANS) equation with Lam Bremhorst low Reynolds number k-e turbulence model. A non-Boussinesq variable density approach is used to model the density variations. Simplified Marker and Cell (SMAC) algorithm is used to solve the governing equations on collocated grid with high accuracy compact finite difference schemes. The pressure Poisson equation is solved by bi-conjugate gradient algorithm and time integration is performed with four stage Runge-Kutta method (Rk-4). The results are presented for Grashof number Gr = 1011 and 1012 and Gay-Lussac number Ga = 0.2 and 2. The present model is valid when buoyancy effects are significant in comparison with forced convection effects. The heat transfer characteristics are analyzed by varying forced inlet velocity, inlet port size and inlet port location. The assisting flow enhances plume discharge rate and increases convective heat loss from cavity. The opposing flow weakens thermal buoyancy and minimizes convective heat loss from cavity. The present mathematical model and numerical method are in good agreement with the existing results available in the literature. © 2015 Elsevier Inc.