The Calulation Analysis Of Critical Non-deposit Velocity For Low Pressure Muddy Water Pipeline Irrigation

The critical non-deposit velocity is an important parameter in the design and constructionof muddy water pipeline irrigation engineering.The determination of reasonable pipelinenon-deposit velocity is the key to solve the sediment deposition problem in the muddy waterpipeline irrigation system.According to the characteristics of sediment movement in the muddy water pipelinesystem,we assume that the extra energy loss added by the existence of sediment in wateramount to the need of energy support of sediment suspension based on the suspended loadenergy theory.Then we build the relationship between the muddy water pipeline resistanceloss and the pipeline flow, and use the flow rate of the low point of the muddy water curve ascritical non-deposit velocity.We analyze the influence factors and its tendency of the criticalnon-deposit velocity, and put forward the critical non-deposit velocity formula in the muddywater pipeline. Determine the method for calculating the correction factor and verify theveracity of the critical non-deposit velocity formula by adopting the test data which consistsof6groups of different concentration for muddy water samples under four specifications ofdiameter.Then analysis the difference between the calculation formula of the criticalnon-deposit velocity of this article with other empirical formulas, main conclusions are asfollow:Firstly, The main influence factors of critical non-deposit velocity including muddywater sediment concentration, water delivery pipe diameter, sediment density, particle size,etc.Through the analysis of muddy water pipeline test, we can conclude that the criticalnon-deposit velocity increased as the sediment concentration increases while the pipediameter and mud density keeping unchanged. When the sediment concentration andsediment density is constant, the critical non-deposit velocity increases with pipe diameter;When the sediment concentration and diameter stay unchanged,The smaller the sedimentparticle density, the smaller critical non-deposit velocity; The higher the sediment particlesize distribution of the compactness,,the smaller the critical non-deposit velocity.Secondly, A calculation model of pipeline resistance hydraulic gradient is establishedbased on the suspended load energy theory.we build the relationship between the muddy water pipeline resistance loss and the pipeline flow, and put forward the critical non-deposit velocityformula in the muddy water pipeline.Thirdly,we determine the method for calculating the correction factor, and verify theaccuracy of the critical non-deposit velocity formula by combining with the test data.Themaximum relative error between the calculated values and measured values of is3.063%,which can satisfy the practical application requirements of the low pressure muddywater pipe irrigation engineering.Fourthly,the analysis results of critical non-deposit velocity formula of this papercompared with other five empirical formula show that the formula of this paper has higherprecision.