This study numerically investigated the effects of geometric parameters of chimney weirs on the discharge coefficient (Cd).Here, chimney weirs with apex angles 74°, 84°, 94.4°, 106° and 116° at two crest heights were examined. The RNG turbu-lence model was selected due to its greater accuracy compared to k-ε,k-ωand LES methods for these types of flows. Withincreasing discharge and crest height, the value of Cddecreases. The effect of constant Cdshowed an increase in the percent-age of discharge deviation from the discharge values obtained from numerical solution. Based on dimensionless variablessuch as ratio of water head to the crest height, the ratio of crest length to the crest height, the ratio of the vertical distancebetween weir crest and the first point where the weir slope changes to the crest height, and the vertex angle of the invertedtriangle, non-linear polynomial regression relations were obtained.
