Wall Friction and Boundary Layer Development in the Cone of a Francis Turbine Scale Model

To characterize the boundary layer development, in the cone of the Francis turbine, wall friction and velocity measurements are performed. The mean wall friction measurements evidence the increasing risk of the boundary layer separation at the cone wall with the increase of the discharge. The flow surveys close to the wall evidence a development of a 3D boundary layer under adverse pressure gradient. The analysis of the results reveals that the composite power law of Barenblatt and Chorin is a good approximation for the velocity profiles in the near wall region for the 4 operating points considered.