A model of 90 degree turn oscillatory flow

A 2-D axisymmetric CFD (Computational Fluid Dynamics) model was developed to simulate the UMN test rig with a 90-degree flow turn to a radial flow in a channel between two discs. One case has been examined in this paper, S (Disc spacing) = 0.127 m and Re_D =7600 for both unidirectional and oscillatory flows. The CFD-ACE+ commercial CFD-code was utilized for this study. Three different CFD models were attempted in this paper: a) Laminar, b) K-ω turbulence model and c) K-ε turbulence model. The results from the K-ω model were in much better agreement with the experiment than the K-ε model (not shown in this paper). For unidirectional flows, the K-ω turbulence model shows similar results to the flow visualization including the size and location of the vortex generated in the flow. The laminar flow does not show these flow features at all. In the oscillatory flow conditions, the laminar and the K- ω turbulence models showed similar results. The flow features are predicted reasonably well but the comparison with the velocity measurements are not as good. It seems that we need a model that will accommodate laminar flow in the stagnation region and turn into a turbulent model some distance away from this region. A single model with transition capabilities will be even better.