Novel design of composite broad-crested weir for determining open-channel emissions.

The current study deals with a composite broad-crested weir which is specially designed with the unique idea for a 'constant discharge coefficient (C_d) of 0.6'. It is investigated experimentally and numerically. The available designs of the weir are unable to give constant C_d over a wide range of discharge as 'C_d' itself is relative to the head over the weir crest. Therefore an attempt is made to restrict C_d value to 0.6 irrespective of the variable head on the weir crest. This is achieved by adjusting the widths of the weir. With the novel objective, C_d is frozen to constant value and instead of it, 'b' is allowed to vary. The weir so designed is capable of producing constant C_d over a wide range of discharge and hence will be helpful from the viewpoint of field applications. Under existing laboratory conditions, the research reports for emissions varying from 20 to 100% of the design discharge. The numerical performance of the CBC weir through FLOW 3D is experimentally validated to examine the crest width effect and head over weir crest. In the experiments, C_d is found to vary proportionally with discharge from 0.518 to 0.648. The R-value is 0.999, with a mean error in discharge measurement being much less.