The Hydraulic Characteristics In Siphon Tunnel Of Dockyard

The siphon passage system has been widely adopted in newly built large-size dockyard in recent years. On the basis of current research situation, the theoretical analysis, model test and numerical simulation are all applied to research hydraulic characteristic of siphon passage to solve the engineering problem that we concerned. And the main research content and conclusion are as follow:Aiming at hump suction pressure of siphon passage in engineering practice, the motion equation of siphon flow is built in cylindrical coordinates system and analytic expression of velocity and pressure at hump section were derived. And it is proved that the pressure expression was consistent with experiment data from the model test for siphon passage system of1#Longxue dockyard. Based on the pressure expression, a new calculation method of the optimal radius at siphon section was proposed, and several groups of the optimal radius at different flow rate and hump pressure are calculated with the new method, whose results of hump pressure is more homogeneous compared with that of predecessor. It is indicated that the centrifugal force is well utilized and it is good to prevent the occurrence of cavitations.The dimensional analysis for siphon course in hydraulic model test is made with π theorem, and it is drawn that the similitude between siphon formation time in model test and prototype can be existed unless the follow conditions must be satisfied:(l) The model text must be in depresuring environment with1/λ of atmospheric pressure (2) The effective pumping speed of model text must be1/λ2.5of prototype. It is difficult to realize the depressurizing environment in model text.The theoretical model for siphon course whose reliability is demonstrated by simplified experiment can be used to forecast siphon formation time. With the hydraulic model test of siphon passage in2#dockyard of Dalianshipbuilding industry, the three-dimensional numerical simulation model wasbuilt up to study the hydraulic characteristics of siphon passage system,Bychanging water level boundary into pressure boundary and disposing the exitboundary with VOF, it can be realized that the covering volume is forecastedwith high precision and the defect that flow rate or velocity boundary must beset on basis of model test data in past numerical calculation can be avoided.Based on the calculation results, it is drawn that the double passage structure ofthe guide wall blocked conveyance capacity of passage and lead to the high flowvelocity of the right passage. It should be removed to improve the flow conditionand balance the flow rate of left and right passage and the structure of doubleinlet siphon passage are optimized, which lead to the maximum flow rate isincreased by35%and can effectively reduce the irrigation time.