Multi-jet impingment cooling on a concave surface, under stationary and rotating conditions

This study focuses on the prediction of the flow and thermal development, when cooling fluid form a row of five jets impinges on a heated concave surface of a semi-cylindrical cooling passage. The passage can rotate about an axis normal to it and parallel to the jets. This application is relevant to the internal cooling of the leading edge of turbine blades. The objective is to establish how reliably the flow and thermal characteristics can be predicted, using a commercial CFD package. The FLUENT code is employed for this purpose and three sets of computations have been obtained, one for stationary and two for counter-clockwise rotating conditions. A variant of the k- turbulence model is used, with a two-layer near-wall treatment. The jet spacing (jet distance to jet diameter ratio) is 4 and ratio between the radius of the concave surface and the jet diameter is 3.125. The flow Reynolds number, based on the jet velocity and diameter (ReVjdj/) is 15,000 and the fluid Prandtl number is 6.09 (water). For the rotating cases examined, the rotation number (Rodj/Vj) is 0.09 and 0.18. The effectiveness of the predictions is assessed through comparisons with local flow and thermal measurements, produced by the authorsf group. For the stationary case, the local flow development within the passage and also the local Nusselt number over the concave surface are well reproduced. The heat transfer comparisons for the rotating cases do not show the same degree of agreement between predictions and measurements.