Hydraulic characteristics of free fall water in open channels and its application in flow measurement
[Objective]As an effective facility for connecting the upstream and downstream water flow of open channels,open channel drop water can be applied to open channel flow measurement.By simply measuring the depth of its drop bucket section,accurate measurement of its flow can be achieved.[Methods]An analysis and comparison method is used to summarize the re-search result of free fall in open channels both domestically and internationally.The comparative analysis is conducted from three aspects:hydraulic characteristics of free fall in open channels,experimental research on water drop in open channels,and theo-retical research,[Results]it was found that the research on the hydraulic characteristics of free falling water in open channels mostly focuses on the pressure distribution at the section of the falling bucket,the research on the water drop test of open chan-nels focuses on the influencing factors(channel bottom slope S,roughness n,channel width,channel section form,Froude num-ber,etc.),which can be obtained based on energy equation,momentum equation,N-S equation,and other numerical simula-tion method.[Conclusion]The result indicate that the value of he/hc in the experiment is basically a constant in rectangular channels,but this conclusion has not been verified in other cross-sectional forms of channels;this value is related to the bottom slope S and roughness n of the open channel,and research on the bottom slope is mainly focused on gentle slopes(S=0.002 6～0.097 3)channels,with less research on steep slopes and less on flat slopes.The research range of roughness n is 0.009 3～0.045 0,but in actual engineering,the value of n varies greatly.Therefore,it is necessary to further verify the values on other forms of channels and study the relationship between the values and the bottom slope S and roughness n on a larger scale,which is more conducive to the promotion and application of open channel drop water technology.
free fallhydraulic characteristicsflow measurementdepth in fallingcritical depthinfluence factor
万方数据
维普
