FLOW VISUALIZATION STUDY FROM A FLAT PLATE WITH MULTIPLE IMPINGING JETS FOR DIFFERENT CROSS-FLOW SCHEMES

A flow visualization study has been carried out computationally on a flat plate with a 5x5 array of impinging jets for different cross-flow schemes. The k-ω SST turbulence model is used for carrying out the RANS simulations. The parameters investigated are (i) cross-flow schemes (minimum, medium & maximum), (ii) jet-to-plate spacing (H/D = 1, 2, 3 & 5) and (iii) turbulent jet Reynolds numbers (15000, 25000 & 35000). The topology and three-dimensional separation phenomena are used to explain the flow and heat transfer characteristics. The skin friction lines on the interaction surface are explained with the help of nodal points of attachment and separation, saddle point, separation, and attachment lines. It is observed that the skin friction lines change their pattern with H/D and cross-flow. Peaks in the heat transfer are observed corresponding to the impingement point and wall jet interaction points. At lower H/D values, the effect of cross-flow is more prominent. However, these effects are marginal for higher H/D values. For lower H/D, the localized heat transfer rates are high but the uniformity in heat flux is obtained with an increase in H/D. In maximum and medium crossflow cases, the heat transfer pattern changes with the distance from the center of the plate. It is found that the flow structure on the surface is independent of the jet Reynolds number.