LBM study on unsteady flow and heat-transfer behaviors of double-row film cooling with various row spacings

Abstract

A series of large-scaled simulations of double-row film cooling are performed by using hybrid thermal lattice Boltzmann method (HTLBM) and multiple Graphic Processing Units (Multi-GPUs) to capture the detailed flow dynamics and heat-transfer features. This paper mainly focuses on the multiple interactions among jet flows with various row spacings and crossflow. The effect of row spacing l on the unsteady film cooling characteristics is also analysed. The row spacing is set as l=3D,5D,7D,9D,12D. Here, D is the diameter of cooling hole. The coolant jet with a typical blowing ratio of BR=0.5 is injected at a streamwise inclined angle α = 30° into a turbulent flat plate boundary layer profile at a free-stream Reynolds number of Re=4000. The simulated results show that the flow and heat-transfer behaviors in double-row film cooling vary much with row spacing due to different mixing characteristics among jet flows with various row spacings and crossflow. The multiple interactions among jet flows and crossflow change the integral form of coherent structures and the characteristics of counter-rotating vortex pair (CVP). The generation of the secondary and tertiary CVPs with the same direction as that of the primary CVP can be observed in the case of small row spacing. While, the secondary CVP changes its rotating direction and the tertiary CVP even disappear as row spacing increase. Therefore, the detachment of coolant jet becomes weak and the coverage of coolant film enlarges when the row spacing is large. The overall cooling performance is good at l=9D and l=12D.