Whole-field visualisation and velocity measurement of an instantaneous transonic turbine flow

The work described in this paper represents a premiere in the application of Particle Image Velocimetry (PIV) to turbomachinery flows. This technique allowed the visualisation of the instantaneous transonic flow in the inter-blade passage of a rotating annular cascade at engine conditions. By means of photographic recording of flow tracers and specialised image processing, the instantaneous velocity over the whole field was measured with estimated accuracy between 2 and 5%. Furthermore, the vorticity map was created by means of differentiation and linear interpolation on a Delaunay triangular grid. From the superposition of sequential frames, a steady state velocity map was reconstructed.