Application of Bottom Axis-driven Overflow Weir on the Moat in Suzhou, China

As a combination of weir and lock, the bottom axis-driven overflow weir has both the regulation of gate and discharge capacity of weir, which is controlled by the bottom axis using electricity. The range of regulation is between 0^o to 90^o opening degree. Usually, it likes a sharp-crested weir when it stands upright (opening degree is 90^o) and a broad-crested weir when it lies down (opening degree is 0^o). With simple structure and convenient construction, especially superior fit and high integration with the urban water environment for low head, this kind of weir has an edge of improving hydrodynamic condition of river networks in plain area in urban. The bottom slope rate of the river network at the Taihu Plain is only one-thousandth, and in Suzhou City, it reaches even one in ten thousand. Artificial water potential energy has become an effective means of ameliorating the hydrodynamic condition of river networks. Owning to head difference between north and south, the bottom axis-driven overflow weir is more adoptable to the moat in Suzhou City. As a new weir type, its discharge capacities, geometry and scouring downstream have been studied as it works at an opening degree of 0^o and 90^o. However, no direct outcome was then reported on the effect of flow upstream and head difference of this weir on the change rules of water head and velocity as it runs between 0^o to 90^o. What’s more, the water distribution project has higher demand for head difference because of flood control standard in plain area and development of city. This research presents hydraulic characteristics of the bottom axis-driven overflow weir, based on a 1:12 scale sectional model of Loumen Weir. The main contents of study are as follows: ①Overflow capacity and discharge coefficient. ②Change rules of water head and velocity with the change of inflow conditions and head difference. ③Effect of overflow weir scheduling time on flow regime. A bottom axis-driven overflow weir with properly geometry parameters is running at the Loumen through this experiment. The application of the bottom axis-driven overflow weir in the moat has greatly promoted the hydrodynamic condition and the water environment of river network in Suzhou City in recent years.