An experimental study of flow over V-shape crump weir crest

Abstract

Weirs are considered important structures controlling flow conditions and measuring flow rates in open channels. Crump weir represent good solution tool to control flow depth in streams, especially where controlling fish zones is required. However, installing crump weirs in rivers and relatively wide streams may be accompanied with difficulty of controlling same water level over the entire weir crest length. This study aimed to modify the crest of crump weir to be V-shaped rather than normal crest. Four wooden crump weir models were adopted. Each of the four models had longitudinal equilateral triangle section with the same horizontal base length, L (78.5cm), width, W (29.5cm) and height, P (20cm), but they differ by the middle crest height, P' as (20, 17.5, 15 and 12 cm) according to models 1, 2, 3 and 4, respectively.. The three v-shaped crested crumps and the normal crump were subjected to eight flow rates and five flow depths at steady state modular flow conditions. Data gathered were used to conclude a nonlinear multiple regression formula of discharge coefficient for the modified models tested. The formula concluded was calibrated and verified with very good determination factor (0.958). Effect of crest modification on water level was clear at relatively low flow rates and vice versa.