Buoyancy driven flows have always been, and still are, difficult to model using CFD programs. Much validation work is required along with guidelines for the CFD practitioner about how to model such flows. This paper makes a contribution to these two areas by considering buoyancy driven displacement ventilation in a very simple geometry. The nature of buoyancy driven displacement ventilation is briefly described and guidance offered on how to represent the problem in a CFD program. Simulations were carried out using two eddy viscosity turbulence models. The results show good qualitative agreement with experimental data and analytical results but small discrepancies in some of the quantitative results.