Supercritical flow profile improvement by means of a convex corner at a bend inlet

Abstract

A novel method for the reduction of wave height along the outer wall of a bend is introduced by adding a convex corner to the inner bend wall. The negative waves emitted from the convex corner are then superimposed on the positive waves caused by the outer bend wall. The interaction of positive and negative waves transforms the original single-humped wave along the outer wall to a lower double-humped wave. The optimum expansion angle of the convex corner is a function of the offset width to the bend width, the radius of curvature to the bend width, and the approach flow Froude number. Numerical studies indicate that the convex corner may be used in a wide range of safe conditions free from cavitation damage. By using an optimized convex corner, the wave height may be reduced between 10 and 45%.