This paper compares different turbulent models for unsteady flow predictions for axial flow in a single rod channel configuration. The numerical analyses are carried out using the Reynolds Averaged Navier Stokes (RANS) equations and three different turbulent models. The predictions are compared with available experimental results. The three models considered in the present work include the RNG (Renormalization group) k-ε model, the realizable k-ε model, and the Reynolds stress model (RSM). With each model, an unsteady approach commonly referred to as URANS (Unsteady Reynolds Averaged Navier Stokes) solution is used. Predicted results are compared with available experimental results. The predicted time-averaged mean velocity and turbulent stresses are in good agreement with the available experimental results. Flow unsteadiness, which is important for determining heat, momentum, and mass transfer in the gap region, is presented through time histories and spectra of flow and turbulent quantities and their influence on the transportation of fluid across the gap is also explored. The effect of inflow unsteadiness on the solution is explored through comparing the flow field for a constant velocity inlet boundary condition as well as time-varying boundary conditions for the RSM model.

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