We report on an LES (large-eddy-simulations) study of flow and heat transfer in a longitudinal periodic segment of a matrix of cylindrical rods in a staggered arrangement bounded by two parallel heated walls. The configuration replicates the set-up investigated experimentally by Ames et al. (ASME Turbo Expo, GT2007-27432) and mimics the situation encountered in internal cooling of gas-turbine blades. LES have been performed using the in-house finite-volume computational code T-FlowS. Considered are two Reynolds numbers, 10000 and 30000, based on the rod diameter and maximum velocity in the matrix. The unstructured grid contained around 5 and 15 million cells for the two Re numbers respectively. After validating the simulations with respect to the available experimental data, the paper discusses the characteristic vortex and plume structures, streamline and heatline patterns and their evolution along the pin matrix, around individual pins and at the pin-endwall junctions. It is concluded that the convection by organized vertical structures originated from vortex shedding govern the thermal field and play the key role in endwall heat transfer, exceeding by far the stochastic turbulent transport.

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