Abstract:

In a uniform flow, critical bed slope can be used to discriminate the flow pattern. The variation of critical bed slope against flow varies with the section’s shape. The formulas of minimum critical bed slope for three different sections were deduced according to theoretical analysis. The results show that these three sections, i.e. rectangular, circular and U-shaped section all has a minimum critical bed slope #em/em#_Kmin=26.13n²b^1/3,22.335n²d^1/3 and 22.335n²(2r)^1/3 respectively. The variation in flow pattern can be discriminated conveniently by comparing the actual discharge with the discharge when critical bed slope equals the actual bed slope. This method is simpler and more convenient than the method which determines the flow pattern by calculating critical depth and normal depth.