Unsteady pressure measurement and numerical simulations in an end-wall region of a linear blade cascade

Abstract

This contribution describes experimental and numerical research of an unsteady behaviour of a flow in an end-wall region of a linear nozzle cascade. Effects of compressibility (M_mathrm {2,is}) and inlet flow angle (alpha _1) were investigated. Reynolds number (Re_mathrm {2,is}=8.5times 10^5) was held constant for all tested cases. Unsteady pressure measurement was performed at the blade mid-span in the identical position {mathfrak {s}} to obtain reference data. Surface flow visualizations were performed as well as the steady pressure measurement to support conclusions obtained from the unsteady measurements. Comparison of the surface Mach number distributions obtained from the experiments and from the numerical simulations are presented. Flow visualizations are then compared with calculated limiting streamlines on the blade suction surface. It was shown, that the flow structures in the end-wall region were not affected by the primary flow at the blade mid-span, even when the shock wave formed. This conclusion was made from the experimental, numerical, steady as well as unsteady points of view. Three significant frequencies in the power spectra suggested that there was a periodical interaction between the vortex structures in the end-wall region. Based on the data analyses, anisotropic turbulence was observed in the cascade.