Experimental Study on the Influence That Joint Widths of Open Channel Give Frictional Resistance

Abstract

Under promoting the stock management of water facilities, roughness coefficient becomes the important index in the hydraulic performance diagnostics of the concrete open channel. However, in the in-use open channel, roughness coefficients calculated from flow velocity and depth measurement are inaccurate. Therefore studies to identify the roughness coefficient from the arithmetic average roughness of the open channel wall have proceeded. However, there are joints at equal distance in the open channel. Joints may affect the frictional resistance of the open channel. In this study, we examined the influence that joint widths of the open channel gave frictional resistance by model channel flume experiments which consisted of three kinds of different roughness walls. As a result, the water depth decreased in and around the joint, and it recovered near the middle between joints. On the other hand, the frictional resistance of the open channel did not depend on the joint width which are 0 to 2.2% of one span in the three kinds of model channel flume experiments.