Supercritical Expansion Flow in Rouse Modified and Reversed Transitions

Supercritical expansion flow in nearly horizontal rectangular channels is actually based on the Rouse wall geometry. As the transition structure becomes extremely long, a revised design involving significant shortening is presented. The revised design is based on separate observations of the flow in the abrupt expansion, and two alternative designs, i.e. the modified and the reversed Rouse wall curves. The modified Rouse wall curve is found to give no improvement over the abrupt expansion and is thus dropped. The reversed Rouse wall curve yields better flow conditions than the abrupt expansion and is significantly shorter than the original Rouse curve. The semiempirical approach accounts for the effects of streamline curvature and viscosity. The free surface is shown to be governed by the Froude similarity law; the velocity field involves significant Reynolds effects in addition. Thus, the latter may not be analyzed by a generalized approach. The surface of flow may further be analyzed when using a correctly distorted coordinate system. Thus, insight is given in the surface profiles along the expansion axis and the side wall. Design recommendations based on the reversed Rouse wall curve end the paper.