Free-Surface Flow over River Bottom Sill: Experimental and Numerical Study

This paper reports on a laboratory study that was performed in an experimental model in the Technological Educational Institute of Thessaly. The current research work examines the water surface profile variation in abruptly altered open channel topography. The objective is to investigate the effects of river bottom sills on flow depth for river control protection against floods. A rectangular bottom sill with one edge rounded was placed on the bottom of a rectangular, horizontal, laboratory open flume and measurements were performed of free-surface flow depth over the bottom sill, under steady flow conditions, for different inflow discharges. Moreover, the HEC-RAS simulation model was used to numerically simulate the water surface variation over the rectangular bottom sill, under steady flow conditions. A mixed flow regime simulation was performed in order to validate the transition from subcritical to supercritical flow conditions. The computed flow depth variation over the rectangular bottom sill was compared with the obtained experimental measurements in order to demonstrate the accuracy of the performed measurements. The presented experimental data may be used to assist in the development of new and the verification and refinement of existing river hydraulic numerical simulation models, particularly those which use non-hydrostatic pressure distribution. © 2015 Springer International Publishing Switzerland.