LES of Impingement Heat Transfer on a Concave Surface

Abstract

Wall-resolved and zonal numerical large eddy type simulations are performed for a round jet impinging on a concave hemisphere at Re = 23,000. The zonal method uses a near-wall k–l model and a Hamilton-Jacobi equation to match this to the large eddy simulation zone. To minimize numerical dissipation, a self-adaptive discretization (SDS) scheme is examined. Both second- (n = 2) and sixth- (n = 6) order-based central discretization schemes are tested. The characteristics of the schemes is assessed using two test cases: the development of a subcritical Tollmien-Schlichting (T-S) stability wave in a plane channel and the decay of homogenous, isotropic turbulence (DHIT). It is found, that Smagorinsky LES simulations tend to be too dissipative in the high wave-number region, even with the SDS scheme; hence, the SGS model is omitted. Significant flow feedback is observed for the hemisphere case. Both shear-layer excitation and stabilization is observed. Computed wall pressure coefficients for the zonal NLES method are encouraging; for the wall-resolved case the stagnation region value is overpredicted. Heat transfer for the wall-resolved and zonal large eddy simulations are encouraging. For both quantities the difference between the n = 2 and n = 6 schemes is small, and the modeling approach used appears to be more influential. It is concluded that the presence of feedback mechanisms should be considered when designing experiments and/or numerical simulations for this case, and that the importance of boundary conditions for LES should not be neglected.