Author(s): K. Keshava Murthy; C. Rangaraj

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Abstract: This paper presents a generalised theory and design of a new class of self basing weirs of constant indication accuracy giving a discharge α(head) n for 1/2 s ≤ n ≤ 3/2. Unlike in the earlier designed compound weirs for n < 3/2, (eg., Sutro weir) the weir is defined by a single profile throughout and a portion of the weir above the crest acts as a base. Single profile weirs eliminate the source of error associated with compound weirs arising from the assumption of single value of coefficient of discharge (C d ) for both the base weir and the complementary weir above whereas two separate C d s' should be used. The depth of the base weir can be reduced by altering certain parameters to suit the practical considerations. The discharge through this weir for all flows above a threshold depth “d” and depth of flow “h”, is proportional to h n ; 1/2 ≤ n ≤ 3/2; within a prefixed allowable error of ±1%. The problem is approached by using a hyperbolic function as the discharge generating function. The generalised design presented in this paper allows balancing between the contradictory requirements of accuracy and reduction of afflux in the field. Experiments with three weirs for n = 2/3, n = 3/4, & n = 5/4 confirm the theory by giving a constant average coefficient of discharge for each weir.

DOI: https://doi.org/10.1080/00221689809498616

Year: 1998