Aerodynamic performance investigation of a Rib Roughened Cooling Channel Flow with high blockage ratio.

The present study deals with a detailed experimental investigation of the turbulent flow inside a rib-roughened turbine blade cooling channel. The main objective is to enhance the understanding and deepen the analysis of this complex flow field with the help of highly resolved Particle Image Velocimetry aerodynamic measurements. These measurements also constitute the necessary complement to the already reported wall heat transfer distributions. In this way, a wide and reliable data base is also made available for numerical code validation. In addition, a coherent structure eduction is performed by means of a wavelet approach in the symmetry plane of the channel. This analysis allows to draw additional conclusions about some of the measured turbulent structures. The measurements are carried out at correct Reynolds number within a scaled up model of a stationary straight cooling channel, with turbulent promoters (ribs) installed on one wall. These ribs present a high blockage ratio (30 %) and are perpendicular to the “mean ” flow direction. A global three dimensional view of the velocity field is provided by applying the PIV technique in between two consecutive ribs along different and mutually perpendicular planes. The highly resolved data allow a very exhaustive description of a number of particular flow structures. The combined analysis of both aerodynamic and heat transfer results puts in evidence the role of the mean and fluctuating flow features in the heat transfer process