URANS computations for a complex internal isothermal flow Original Research Article

Unsteady Reynolds Averaged Navier–Stokes (URANS) computations for an idealized electronic system are considered. Comparison is made between new Laser Doppler Anemometry (LDA) measurements and finite volume predictions involving nine turbulence models. Zero, one and two equation models are tested. Some of these utilize zonal methods and one, non-linear eddy viscosity relations. For velocity components, reasonable agreement is found between measurements and predictions. Overall, the zonal models gave an average error of just less the 15% when compared to velocity measurements. The measurements have an estimated ±5% error. The turbulence models are found to give dramatically different turbulence intensities. These, in turn, give significant variations in the predicted temporal behaviour. Unlike, as suggested by measurements, predicted unsteady flow component amplitudes are found negligible relative to stochastic turbulent components. For velocities, the accuracy of the standard k–ε model is found worse (by around 4%) than that of a simple mixing length model. Results suggest the former is excessively diffusive. Overall, the zonal models show greatest accuracy. However, for intensities, even these predictions differ significantly (on average 28%) from measurements.