عنوان مقاله [English]
In this research, the effect of submergence on the discharge of flow over the sharp-crested weir with an arc in the plan and toward upstream is investigated. This research was conducted on the physical model with twenty different samples of the sharp-crested circular weirs including four different arc lengths (or arc angle), each with five different heights. In these experiments, flow analysis has been carried out for the submergence conditions of the weir. The effect of submergence magnitude on discharge rate of circular weir to find a relationship for determination of this effect was the effort of this study. Examining the submergence conditions for these types of weirs proved that the general equation derived from previous research (Villemont equation, 1947), is not valid to the circular weir. Villemont Eq. produce an error between zero to 50% and an average of 14% for various laboratory experiments. Therefore, a modified equation for submergence conditions of this type of weir was proposed. This equation in different experiments yields an error between zero and 17% and an average of 4%.