Experimental Study of Flow Regimes of Stepped Weir

Abstract

Depending on the discharge and the stepped weir's dimensions, flow over a stepped weir can be primarily divided into three different flow regimes: nappe, transition, and skimming. The different properties for each flow regime make the decision of the flow regime an important component in the design of a stepped weir. Five stepped weir models have been used in experiments to determine the flow regime limits for these weirs. The models were made with various numbers of steps (3, 5, 7, 10, and 14) and downstream slope angle of 30˚. The configurations of steps that tested were flat step, fully pooled step, and zig zag pooled step . The results showed the end sills have a large impact on the type of flow regime. Based on the experimental data for flow regimes (nappe flow , transition flow and skimming flow ), a new set of empirical equations was proposed, with a determination coefficient〖 R〗^2 for these regimes (0.87, 0.71 ,0.7 ) respectively.