Counter-rotating streamwise vortex formation in the turbine cascade with endwall fence

The three-dimensional turbulent flows in the turbine cascade with and without endwall fences are numerically investigated by solving the incompressible Navier-Stokes equations with a high-Reynolds number k-e turbulence closure model. The limiting streamline patterns and the static pressure contours at the suction surface of the blade as well as on the cascade endwall are employed to visualize the effectiveness of the endwall fence for the secondary flow control. The analysis on the streamwise vorticity contour maps along the cascade with the three-dimensional representation of their iso-surfaces reveals the complicated structures of the vortical flows in the turbine cascade with endwall fence, and also leads to an understanding on the formation of a counter-rotating streamwise vortex over the fence. The mechanisms of controlling the secondary flow and the proper selection of an optimal fence height are also explained.