Large-eddy simulation of non-isothermal flow over an array of cylinders placed inside a converging channel

Abstract

This work evaluates the flow and thermal characteristics of a gas-turbine blade trailing-edge. The study is carried out using large-eddy simulation (LES) for Reynolds number, Re=5900. In view of the realistic conditions, a converging channel with a staggered arrangement of fins with varying aspect ratio is considered for the higher pressure of the coolant and the larger temperature difference between the blade and the coolant. The present results are compared with the parallel channel case to identify the effects of converging flow passage of the channel on the flow and thermal characteristics. The computational setup and methodology are thoroughly validated using reference data from experiments as well as LES available in the literature. The results are analyzed in terms of Q-criterion, streamlines, vorticity and turbulent heat flux contours, and the Nusselt number profiles at several locations in the flow domain. The present results shows, unlike in the parallel channel case, a dominant spanwise component of velocity that helps in the formation of a strong vortex behind the first row itself, and the Nusselt number consistently increases from the first to the last row. The maximum gain and diffusion of turbulent heat flux occur within a recirculation zone and along the free-shear layer, respectively. The heat flux from the end-wall is extracted mainly by the spanwise velocity component, which is also responsible for its advection to the central region. Heat transfer is observed to be higher from fins compared to the end-walls, which underscores the importance of the active participation of fins in the analysis of heat transfer at the trailing-edge.