Simulations of Film Cooling Flow Structure and Heat Transfer in the Near Field of Cooling Jets With a Modified DES Model

Abstract

Abstract Simulations of film cooling in the near field (x/D < 15) of coolant jets on a flat plate are carried out with detached eddy simulation (DES) and modified DES models. The time-averaged unsteady film cooling effectiveness is compared with experimental data. Both models use two-layer zonal model for near-wall treatment. The near field critical turbulent flow behaviors such as mainstream entrainment, spanwise spreading of counter rotating vortex pair (CRVP), and vortical structure evolutions are predicted and analyzed by DES and modified DES in this study. Modified DES model differs from the DES by implementing an increased eddy viscosity in the spanwise direction to enhance spanwise-diffusion of film cooling jets. Detailed comparisons of DES and modified DES modeling results are made under density ratios of 2.0, 1.6, 1.2 and blowing ratio of 1.0 for a single hole. Modified DES model predicts a wider spanwise spreading of temperature field and film cooling effectiveness. In a comparison of spanwise-averaged film cooling effectiveness with experimental data, DES and modified DES models predict 14.8% and 10.4% deviations under density ratio of 2.0. For density ratio of 1.2, the DES and modified DES results deviate from data 24.5% and 14.7% respectively. Then simulation of film cooling with a three hole domain is also carried out. Instantaneous effectiveness results show that the jets from nearby film cooling holes start to interact with each other before x/D < 10. When the interactions of flow from film cooling holes next to each other are strong, simulations using several cooling holes are meaningful and the current study shows the difference of multi hole and single hole simulations.