Stage-Discharge Relationships of Broad Crested Weir for submerged Flow Condition Utilizing Incomplete Self-Similarity(ISS) Technique

Abstract A broad-crested weir is one of the simplest and oldest hydraulic structures.It was used to measure flow regulate flow depth and control flood passage. Open channel flow measurement requirements are based on the experiments performed to evaluate the empirical discharge coefficients and equations. The aim of this study is to develop the stage-discharge relationships using incomplete self-similarity theory and traditional methods for calculating the discharge coefficient (Cds) and to determine which method is the most effective. All experiments were carried out in a channel  with a cross-section of (0.5 × 0.5) m and a length of 15 m. 125 experiments were carried out on 25 physical models of a broad crested weir with a rounded edge, under submerged flow conditions. The results showed, after comparing the two methods, and by calculating the mean absolute relative error (MARE) for discharges . It is equal to (4.25%) using the incomplete self-similarity theory, and it is equal to (7.05) by using the traditional method. Thus, the incomplete self-similarity formula is more accurate than the other method.