Modelling of EMC screens for radio base stations. Part 2: Evaluation of turbulence models

For pt.1, see ibid., vol.I, no., p.463-70 (2004). The objective of this paper is to investigate the performance of five well-known turbulence models and two wall treatments, in order to predict the details of the flow patterns through an EMC (ElectroMagnetic Compatibility) screen. The turbulence models investigated in the present study are four different eddy-viscosity models; the standard k-ε model, the renormalization group (RNG) k-ε model, the realizable k-ε model and the k-ω model, as well as the Reynolds stress model (RSM). The commercial finite volume code Fluent 6.1 was used for simulation. A steady-state three-dimensional model, which serves as the most accurate representation of the model, was used in order to predict the details of the air-flow paths and pressure field. The flow was assumed to be isothermal, turbulent and incompressible. The numerical predictions were validated experimentally by using wind tunnel measurements and smoke visualization. The performances of the turbulence models are discussed and the RSM results are compared with other two-equation turbulence models. The result shows that for most of the tested turbulence models with the right wall treatment, the influence on the prediction of pressure drop and the velocity field is not large. The pressure field is over predicted about 15% and the velocity average deviation at several locations before and after the screen is less than 10%. Simulations using a hydraulic impedance surface, i.e. without a detailed modelling of the EMC screen, show that the pressure field is also over predicted and great differences are observed in the velocity field.