Application of Modified Boussinesq Equations in Predicting Discharge Coefficients of Trapezoidal Broad Crest Weirs and Producing Rating Curves

For Trapezoidal weirs most of the proposed discharge coefficient relationships have been obtained experimentally. Also، some theoretical relationships have been proposed based on ignoring the streamline curvature and considering the hydrostatic pressure distribution. In this paper، a numerical model was developed for recently proposed Boussinesq type equations which incorporated the streamline curvature with considering the non-hydrostatic pressure distribution for unsteady flow conditions. The model was employed to determine the discharge coefficient of trapezoidal broad crested weir، the results of which were compared with the compiled experimental data and with available relations. The results showed that the discharge coefficient computed by Level 4 equation، had presented higher accuracy in comparison with the experimental relation for the tested crest weirs. Also modeling these equations was easier compared to the three-dimensional models. These equations could be incorporated with the available one-dimensional of models to produce rating curves and to design water measurement structures for a continuous flume invert.