Wall cooling effect on separated flow transition over a highly loaded compressor blade

Abstract

Large eddy simulations (LESs) were conducted to investigate the effects of wall cooling on the separated flow transition over a highly loaded compressor blade at two Reynolds numbers of 2.0 × 105 and 1.0 × 105. The locations of transition onset and completion were identified by linear stability theory (LST). As the transition was triggered, the streamwise gradient of the near-wall temperature increased to a higher level. Therefore, the transitional region can be roughly diagnosed through the distribution of temperature. Results showed that wall cooling weakened the relative role of turbulent dissipation in suppressing rapid amplification of disturbances, which promoted the transition process and reduced the length of the transitional region. Compared with the case of the adiabatic wall, the scale of three-dimensional vortex structures on the cooled wall was reduced, and the vortex rolling-up and breakdown were weakened. For such conditions, the region of high-level Reynolds shear stresses shrunk and the loss generation rate declined. By comparison, the effect of wall cooling on controlling the transition process was more pronounced at a lower Reynolds number, and the profile loss was reduced by 18.23% and 25.05% at Reynolds numbers of 2.0 × 105 and 1.0 × 105, respectively.