Hydraulic Characteristics Of Pressure Pipeline

With the development of economy,the increase of population,the improvement of urbanization level and the acceleration of urban and rural integration process,the contradiction between supply and demand of water resources will be increasingly prominent.Irrigation water consumption accounts for 65%of the total water consumption,which is a main water-saving battlefield.Pipe irrigation water conveyance project reduces water seepage and evaporation loss,so the water use coefficient is higher than that of general channels,with advantages in higher water transportation efficiency,less area and easy management.It is becoming one of the important ways to save water in agriculture.Pressure pipeline is the important part in pipeline irrigation system,whose total investment makes up 65%⁸0%of the system.In addition to rigid polyvinyl chloride?UPVC?pipes,concrete pipes,ductile cast iron pipes,polyethylene?PE?pipes with clear hydraulic characteristics,there are glass tubes,bamboo pipes,multiple new pipes such as strengthened steel composite pressure pipes.This paper,by means of indoor tests,combined with the related knowledge of hydraulics deals with the hydraulic characteristics of cement lined ductile cast iron pipes,bamboo winding composite pipes and polyvinyl chloride?PVC?pipes.The main findings are as follows:1)the hydraulic characteristics of cement mortar lined ductile cast iron pipesThe yield of roughness?K?of the cement mortar lined cast iron pipes negatively and linearly correlates with the logarithm of Reynolds number and the relation curve is:K=199.55?lgRe?^-4.876;R²=0.9962.The coefficient of frictional head loss of pipes???decreases with the increases of pipe flow,the relationship is a quadratic function and the function expression is:?=0.1084 Q²-0.0513Q+0.0168;R²=0.9764;With the increase of pipe flow,the coefficient of hazen William?Ch?increases but it is stable between 153.2741 and 166.8392.Polynomial fitting was carried out on the coefficient of hazen and Q:C_h=197.64 Q²+116.54 Q+149.83;R²=0.9815.The measured value of n increases with the increase of Q but it is basically stable between 0.007441 and 0.009225.N can be a quadratic function of the fitting for Q:n=0.0307Q²-0.0166 Q+0.0166;R²=0.9902.The corresponding calculation formula of pipeline frictional head loss is:???.If the pipe diameter is 300 mm,and the pipe flow is0.041⁰.264m³/s,the average value of?is 0.012.The average value of the Hazen William coefficient?C_h?is 162.24.The average value of Manning roughness?n?is 0.008.2)the hydraulic characteristics of bamboo winding composite pipesThe amplitude of the measured equivalent roughness?K?of Bamboo winding composite pipes is bigger,from 0.0549032 to 0.107122,which is negatively and linearly correlates with the logarithm of Reynolds number.The fitting curve of K and lgRe is available after quadratic fitting:K=0.0772?lgRe?²-0.9096?lgRe?+2.7388;R²=0.9578.The coefficient of frictional head loss of pipes???decreases with the increases of pipe flow,and the relationship is a quadratic function.Lambda function can be expressed as related to Q:?=0.4551Q²-0.1469Q+0.0274;R²=0.8889.The coefficient of Hazen William?C_h?increases slightly with the increase of the pipe flow but it is stable between 121.5967 and 138.2771 and levels off with the increase of the pipe flow.The coefficient of Hazen can be expressed as the function related to Q:C_h=483.1 Q²+172.74 Q+122.93;R²=0.5642.When the pipe flow is greater than 0.07 m³/s,the coefficient of hazen William is almost a constant,137.056.The measured value of n increases with the increase of Q but it is basically stable.The measured values are between 0.008882 and0.011422.N can be a quadratic function of the fitting for Q:n=0.0608 Q²-0.0256 Q+0.0256;R²=0.8731.The corresponding calculation formula of pipeline frictional head loss is:???.If the pipe diameter is 300 mm,and the pipe flow is 0.042⁰.253 m³/s,the average value of lambda is 0.017.The average value of the Hazen William coefficient?Ch?is 137.The average value of Manning roughness?n?is 0.00956.3)hydraulic the characteristics of PVC pipeThe equivalent roughness?K?of PVC pipelines is negatively correlated with the logarithm of Reynolds number,and the measured equivalent roughness varies significantly from0.0000360201 to 0.0198413019.The coefficient of frictional head loss of pipes???decreases with the increases of pipe flow,and the relationship is a exponential function:?=0.0012 Q^-0.697;R²=0.9663.The coefficient of hazen William C_h increases slightly with the increase of pipe flow but it is between 54.455 and 138.6418 and leveles off with the increase of the pipe flow.When the pipe flow is greater than 0.015 m³/s,the coefficient of hazen William levels off.The coefficient of Hazen can be expressed as the function related to Q:C_h=28.537 ln?Q?+246.24;R²=0.9845.The measured value of n increases with the increase of Q but it is basically stable.The measured values are between 0.008 and 0.011422.N can be exponential function fitting for Q:n=0.0021Q^-0.349;R²=0.9663.The corresponding calculation formula of pipeline frictional head loss is:???.If the pipe diameter is 101 mm,and the pipe flow is 0.0014⁰.0242 m³/s,the average value of lambda is 0.037.The average value of Manning roughness?n?is 0.011.