Mathematical Semi-analytical Model of Combined Flow over Weir and under Gate by Different Geometries

The most important advantage of applying the combined weir and gate is to maximize its performance
under sedimentation conditions. In this paper, a new mathematical model is presented to determine the
relationship between stage and discharge for structures consisting of the weirs and gates by different
geometries in different flow conditions. Since the geometry of these structures has lateral
compression, velocity distribution in transverse section is not uniform. Therefore, the energy and
momentum correction coefficients should be used, and in this research, these coefficients are
calculated using optimization approach. One great important advantage of this procedure is the use of
relatively simple hydraulic principles. To verify the given method, different combinations of weir and
gate as a physical model are tested in the laboratory. From the laboratory data it is concluded that the
proposed method is capable of calculating stage-discharge relationship by reasonable accuracy.