Abstract
The main objects of this investigation are to obtain convenient expressions for the estimation of discharge coefficient for submerge flow over concave and convex semicircle shape crested weirs. Sixteen weir models were constructed and tested. these, models were classified into four groups. The first and second groups were of single cycles having concave and convex shapes, respectively, with curvature radius of 15cm. The third and forth groups were of double cycles having concave and convex shapes, respectively, with curvature radius of 7.5cm.in each group the weir height, p was varied four times 10cm, 7.5cm, 5cm and 2.5cm Based on results of this study it was found that for constant weir radius, R, the discharge coefficient, Cd, increases with the increase in the relative upstream head, h/p, while, for constant upstream bead, weirs of small heights give higher discharge coefficient than those of large height Two general expressions were obtained for the estimation of Cd as function of, relative upstream head, h/p and relative radius, R/P, one expression for single and double cycle concave submerged weirs and the other for convex submerged weirs.