Hydraulic Performance of Combined Flow Rectangular Labyrinth Weir-Gate

Weirs are common structure to regulate water surface and flow control in water conveyance channel and hydraulic structure. One of effective and economical method to increase the efficiency of weirs is utilization of labyrinth weirs which length of weirs increase with modification of plan form and therefore flow discharge will be increase. Compared to the separate using of weir and gate structures, there are some advantages including the Simultaneous passage of floating substances (wood, ice, etc.) and sedimentation in using combined weir-gate structure. The Rectangular Labyrinth weir-gate is one of the combined models. In this research five physical models that discussion weirs height and effective length changes on discharge coefficient of flow over and under the combined Rectangular Labyrinth weir-gate. Tests were performed on Sari Agriculture Science and Natural Resources University's research flume with width of 0.50 (m) and length of 12 (m) and discharge in range of 10-90 (Lit/s). Comparisons have shown that upstream head water increasing the discharge coefficient reduced. Also discharge coefficient and passed discharge of Rectangular Labyrinth weir-gate are increasing with increase of weir's height (P). Data analysis shows that increase of weir's effective length till H /L (H : Total upstream head, L: Effective length) less than 0.03 lead to increasing in discharge tt coefficient of Rectangular Labyrinth weir-gate. we compared of Rectangular Labyrinth weir-gate with sharp crested weir-gate. The results have shown that till a boundary of current (H /P<0.4) amount of discharge t coefficient of Rectangular Labyrinth weir-gate is almost equal to or more of discharge coefficient of sharp crested weir-gate.