The PIV Experiments On The Forebay Of Pumping Station With The Side Intake Channel

The layouts of the pumping stations include two different kinds of forms which are the front-inlet and side-inlet according to the different patterms of the inlet flow. Usually the prior choice of inflow form in pumping stations is the front-inlet. However, with the restriction of some objective factors such as topographic conditions, some pumping stations have to adopt the side-inlet-form and the water flow from the lateral side is one kind of steering flow which is called bend-flow. In the practical projects, there are several poor water flow patterns in the pumps stations which can deeply effect the performances of the pumps such as deflection, the separation of flow from the wall, the circulation and the vortex ,all of which have adverse effects upon the performance of pumps. In order to smooth the flow pattern of lateral inflow fundamentally, we should lucubrate the discipline of the movements of the bend-flow, and make use of appropriate engineering measures to ameliorate the flow field so as to make the water pump in a excellent inflow state.The small-scale model for the hydraulic model study has the advantages such as low investment, high efficiency and is especially suitable for a qualitative analysis when making a multi-program analysis and comparison. After the development of nearly two decades,the PIV technology has been generally received and is used in more and more domains,which has become a basic test method of researchs of flow field . Taking the forebay of a pumping station as a reference, this paper designs a small-sized experimental device which uses PIV technology to measure the flow field of the forebay and the forebay with measures that can improve the flow patterms .By comparing the two experimental schemes, we get the conclusions that there ere some large-scale circuiting zone and serious drift deflection in the forebay of the side-inlet-form pumping station ;the bottom sill in the forebay does no obvious good to attenuate the the circulation on the surface ,but can ameliorate the drift deflection on the bottom, however, the distribution of flow rate is sometimes uneven in the inlet of pumping station;and if we set a bottom sill in the forebay with a"Y"diversion pier before the sill can attenuate the vortex and bias flow caused by the bend-flow effectively, and homogenize the flow rate making the water enter forward and uniformly and satisfy the requirements of pumps on inflow.It's common to set a bottom sill in the forebay to improve flow patterm,and the length of the flow, that can be adjusted adequately ,is related to the length of the vortex behind the sill.In order to analyze the influences on the length of the vortex behind the sill which are from the flow rate, the depth of water in the front of the pumping stations and the height of the sill,the paper has provided two flow rate , three kinds of depths of water in the front of the pumping stations, five kinds of sill height,Then we combinate them and test the flow field,from the vertical section,of the bottom sill in the eighteen schemes with the PIV .We can analyze the mechanism of improving flow patterm and draw the conclusion that the sill height is the most influential parameter to the length of the vortex behind the sill which is also effected by the flow rate and the depth of water in the front of the pumping stations to some degrees. The bigger the sill height is,the better the average of the velocity of flow could be while the sill height is 0.25-0.60 times of the depth of the water in the front of the pumping station.However the local head loss will increase if the sill is too high.We suggest that the sill should be 0.4-0.55 times higher than the depth of the water when improve flow patterm of the sill.