Summary: We consider the economical prediction of a turbulent oscillatory isothermal flow at transitional Reynolds numbers for an enclosure representative of an idealized electronics system. To assess the accuracy of numerical models, comparison is made with measurements. Normal wall distances, required in some turbulence models, are evaluated using a modified Poisson equation-based technique. Solutions of the Poisson and fluid flow equations are accelerated using multilevel schemes, giving valuable time-savings. The Poisson equation-based wall distance technique is shown to be effective. Zero- to two-equation turbulence techniques are tested, including zonal and nonlinear eddy viscosity models. Of the nine models tested, the zonal models showed greatest potential.