Triangular Board-Crested Weir

The advantages of flow measurement with a thin plate V-notch weir and a broad-crested weir are reviewed briefly. The triangular broad-crested weir is intended to combine the advantages of both in a single structure. The discharge coefficient and limiting submergence are derived from simple theory based on the assumption of critical flow. Details are given for experiments carried out on a weir with a 90○ notch angle and four different lengths of broad crest. It was found that the actual coefficient was less than theoretical and was not constant; however, the limiting submergence agreed exactly with theory, provided the length of the broad crest was at least three times the head. A design curve for the coefficient is included.