We have performed a priori tests of two dynamic subgrid-scale (SGS) turbulence models using a highly resolved direct numerical simulation (DNS) database for the case of incompressible flow ina straight duct of square cross-section. The model testing is applied only to the homogeneous flow direction where grid filtering can be applied without the introduction of commutation errors. The first model is the dynamic (Smagorinsky/eddy viscosity) SGS model (DSM) developed by Germano et al.[5] while the second is the dynamic two-parameter (mixed) model (DTM) developed by Slvetti and Banerjee [2]. As found in prior studies of this sort there is a very poor correlationof the modelled and exact subgrid-scale dissipation in the case of teh DSM. The DSM over-predicts subgrid-scale dissipation on average. Instantaneously, the model provides an inaccurate representation of subgrid-scale dissipation, in general underestimating the magnitude by approximately one order of magnitude. On the other hand, the DTM shows excellent agreement with the exact SGS dissipation over most of teh duct corss-sectionwith a correlationcoefficient of approximately 0.9.
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