Application of a modified algebraic heat-flux model and second-moment-closure to high blowing-ratio film-cooling and corrugated heat-exchanger simulations

The present paper outlines the application of the recently proposed heat-flux model (Mazaheri et al., 2017) to high blowing-ratio film-cooling and corrugated heat-exchanger simulations. Here, the focus is mainly on the accuracy of the predicted thermal fields, while to find out the sources of inaccuracy detailed analysis of the adopted second-moment-closure hydrodynamic model is provided. To do so, fundamental benchmarks which contain the dominant phenomena in the main cases are thoroughly analyzed to identify the anomalies. Then, the main cases including leading-edge film-cooling, antivortex film-cooling and corrugated heat-exchanger are investigated. The numerical predictions indicate that the erroneous evaluation of the surface temperature near the leading-edge stagnation-line, caused by constant Prandtl assumption, is markedly improved through a more accurate prediction of heat-fluxes within the impinging region. In this regards, for a high blowing ratio case, i.e. BR=2, the error in prediction of average adiabatic cooling effectiveness (η‾) is reduced more than 30% and 75% near the first and second row of cooling holes, respectively. In the antivortex film-cooling, the lateral diffusion of the coolant jet, which is essentially depending on heat-transfer between kidney vortices and surface, is reasonably predicted which results in more than 90% error reduction in prediction of η‾ in vicinity of the holes with respect to constant Parndtl assumption case. Also, more than 50% improvement can be observed in predicting the average surface temperature in the corrugated heat-exchanger case, which contains numerous recirculation zones, with respect to constant Prandtl simulations. The results demonstrate that the anisotropic hydrodynamic model may offer potentially improved predictions, however, in order to achieve high level of accuracy, adopting a proper heat-flux model is essential for the high blowing-ratio film-cooling cases which contain highly non-equilibrium flow characteristics.