An Experimental Study of Mobile Boundary Transitions in Alluvial Canals

Abstract

Self-formed shape and energy loss taking place at the transition of alluvial canals were studied. Two trapezoidal erodible canals were modeled along with a sudden contraction in a laboratory flume. Experiments were performed under steady flow conditions for almost-uniform coarse sand with average grain sizes of 1.2, 0.91, and 0.77 mm and flow rates ranging from 0.0001 to 0.0025 m3/s. The results show that the ultimate self-formed warped transition can be represented by an exponential relation that depends on average grain size and flow rate. For a constant flow rate, the length of transition decreases as the grain size increases, whereas for a constant grain size it increases with increasing flow rate, and the minimum energy loss is obtained at the threshold condition.