Application of Tomographic PIV on a Passage Vortex in a Transonic Compressor Cascade

Abstract

The contribution describes the implementation of thick sheet tomographic PIV [Elsinga et al. 2006] in a transonic cascade wind tunnel in order to measure the three dimensional turbulent corner flow in a highly loaded compressor cascade at M1 = 0.6. Under these operation conditions the secondary flow structures in the cascade are dominated by a passage vortex located at the base of the blade and near the suction side. The report describes various aspects of the adaption of the tomographic PIV setup to the restricted access on the cascade wind tunnel. A four camera setup is used to resolve a measuring volume of 36x24x4 mm from which a total of 54x74x13 vectors at a spacing of 0.64 mm in x (chord-wise direction) and a spacing of 0.32 mm in y and z could be recovered. Three dimensional reconstruction of the imaged particle volume is achieved with the maximum entropy reconstruction technique (MENT, [Minerbo, 1978; Bilsky et al.,2012]). The reconstruction quality of experimental data is documented by plots of the reconstructed intensity along volume depth. The extraction of three-dimensional displacement field relies on multi-resolution, 3-D correlation processing with iterative volume deformation. The recovered three-dimensional velocity fields are compared at selected planes with (thin-sheet) stereo PIV data.