A Note on Irrotational Curvilinear Flow Past a Weir

Abstract

Curvilinear flows are commonly encountered in hydraulic engineering practice. Detailed velocity surveys of the curvilinear flow field over a circular-crested two dimensional weir were obtained using laser doppler velocimetry (LDV). Using these test data, the basic assumptions related to the streamline geometry and irrotational of flow over weirs made in all existing theoretical weir models are verified. The test data yielded the pattern, slope and curvature of the streamlines. Water surface profiles were also obtained to determine the depth of flow over the crest and the radius of curvature of the surface streamline at the crest section. As part of the study, the velocity profile of the flow over the weir crest was integrated to obtain the weir discharge coefficient. The weir coefficient obtained on the basis of this empirical procedure is compared with the weir coefficient based on direct discharge measurement.