Experimental Study on the Effect of Roughness Height on the Water Entrainment and Control of Density Current Discharge

In this research the effect of roughness for different bed slopes on the control of sedimentary density current in subcritical conditions was investigated. The results showed that for each bed slope increasing the roughness height had considerable effect on reducing the load discharge of density current front (from 40% to 70% for concentration of 10 g L-1 and 35% to 55% for concentration of 20 g L-1). Also the amount of water entrainment rate reduced with increasing the roughness height (from 50% to 60% for concentration of 10 g L-1 and 48% to 60% for concentration of 20 g L-1). Finally, an equation for predicting water entrainment as a function of Richardson Number and relative roughness was presented. Sensitivity analysis of the proposed equation in this research showed that the effect of Richardson number on estimation of the water entrainment is much more than the effect of relative roughness on it.