Application of various RANS based models towards predicting turbulent slot jet impingement

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Numerical simulation near the stagnation zone for an impinging jet is challenging because of the presence of sharp gradient due to the change of velocity from zero to the system scale velocity. A comparative study of four Reynolds averaged Navier–Stokes (RANS) based turbulence models has been done by numerically simulating a two-dimensional turbulent slot jet impinging air normally on a flat plate. Nozzle-to-plate spacings equal to 4 and 9.2 have been taken as two test cases with nozzle exit Reynolds number of 2×104. The turbulence intensity at the exit of the nozzle is kept constant at 1%. The capability to predict the fluid flow of the standard k−ε model, the low Reynolds number (LRN) k−ε models proposed by Launder and Sharma (LS) and Yang and Shih (YS), and the standard k−ω model have been evaluated by comparing the computational results with the experimental data available in the literature. The numerically obtained results have been compared with the experimental results on impingement surface pressure, free jet mean velocity profiles, spanwise velocity profiles, spanwise distribution of root mean square velocity fluctuation, skin friction coefficient distribution, non-dimensional velocity profile in wall coordinates. The standard k−ε model predicted the largest recirculation loop among the turbulence models used. The skin friction coefficient distribution is reproduced by YS and k−ω model for both the spacings whereas the other LRN model LS and the standard k−ε model are unable to predict the results. The linear law of the wall is found to be valid up to Y+≃4.0 in the recirculation region. The velocity profiles in wall coordinates in the recirculation region are behaving similar to those in the wall jet region of an impinging jet and the developed region of a wall jet.