Boundary layer measurements on the pressure and suction sides of a turbine inlet guide vane

Abstract

Abstract Laser Doppler measurements of shear stress, normal and streamwise mean and fluctuating velocities of the pressure and suction side boundary layers on a turbine inlet guide vane have been made for two turbulence levels Tu. No heat transfer is applied. The transition process is investigated. The blade has a 1.4 m chord. This large chord provides sufficiently thick boundary layers for detailed measurements (down to Y+⩽10, Y+=YUt/ν, Y is the normal to the wall distance, Ut is the friction velocity, ν is the kinematic viscosity). On the pressure side, at the low turbulence level, the onset of the transition occurs at a Gortler number Go=5; while no Gortler vortices have been found. The turbulent state is not completely reached at the trailing edge. At the higher inlet turbulence level, transition occurs at the beginning of the pressure side. The influence of the increase of turbulence is extremely strong on the pressure side compared to that of the suction side. On the suction side, at low Tu, the transition occurs just before a possible separation of the laminar boundary layer. At higher Tu, the beginning of the transition is displaced near the leading edge in a region where the pressure gradient is lower. The transition description is given by the analysis of the development of mean and turbulent quantities.