The research objective of this program is the improvement of turbulent flow modelling in turbomachinery by non-intrusive optical flow diagnostics. Since the flow physics in turbomachinery includes laminar-turbulent transitional flows, rotational forces, fully three-dimensional flows, pronounced pressure gradients in all directions, vortices, secondary flows, subsonic and transonic conditions, unsteady phenomena like wake passing and often two-phase flows (steam and water, gas and particles), the turbine gas flow is an ultimate test for turbulent flow calculation. Differences in predicted and measured efficiencies in turbomachinery are believed to be caused by the empirical input to numerical models still needed to represent the turbulent nature of flow. These differences are large enough that they are not able to replace expensive experimental tests by a numerical calculation process. The proposed program tackles this problem by the application and development of non-intrusive optical diagnostic techniques for turbulent flows in turbomachinery. Within this program these techniques are tested and applied to the transonic test turbine rig at Graz University of Technology.