Numerical Simulation Of Inner Energy Dissipation Of Two Stage Tooth Block

Tooth pier energy dissipation,a new type of the sudden enlargement and sudden shrinkage type energy dissipation which has high energy dissipation,less environmental damage,simple structure and wide application,has been studied in recent years.In the previous work,it mainly apply the physical model test to study the single stage tooth pier energy dissipation in the process of research.In order to further study on hydraulic characteristics of tooth pier energy dissipation,this paper proposes the inner energy dissipation of two stage tooth block.The accuracy of the model was discussed by simulating the single stage inner energy dissipation of tooth block based on standard k-? numerical model as well as comparing with the result of physical model test.And the hydraulic characteristics of two stage inner energy dissipation of tooth block was further studied on the basis of the complete model test to get tooth block spacing andthe area contraction ratio on the influence law of the capacity,energy dissipation,central axis pressure cavitation number and flow field characteristics of pipe flow.The following are conclusions:1.When the flow and tooth spacing are definite,when the area constriction ratio ?₁=0.625,the pressure drop is the biggest,close to 71.9%,and the when the area constriction ratio ?₃=0.375 the pressure drop is the only 14.1%.This phenomenon shows that when the initial flow and tooth spacing is not changing,the smaller the area contraction ratio is,the greater the pressure drop of central axis is.When the area constriction ratio ?₃=0.375,the pressure of central axis is the largest and the drop is close to 31.1% in Q₁=20l/s condition,and the Q₃ =30l/s is opposite in three kinds of flow state,.This shows that when the flow area of tooth block and the spacing are not changing,the greater the pipe flow is,the smaller the pressure of center axis and the greater the drop are.In the plan when the area constriction ratio ?-3=0.375 of three tooth spacing condition,which are 20 cm,40cm and 60 cm,before water flow into the first level,the pressure of the central axis are basically same.After water flow out of the second tooth block,the pressure drop is close to 49.1% in the condition of dental paragraph spacing is 60 cm and the pressure drop is close to 41.6% under the condition of dental paragraph spacing is 20 cm.This is because under the condition of 60 cm,when the water flows through the primary tooth block,the stream turbulence,mixing and vortex are longer,energy dissipation can be more fully and consumes more flow energy,which lead to the largest decline inpressure.The data shows that,when the tooth flow area and the flow rate are not changing,the central axis pressure of the pipes would reduce within a certain range of the paragraph spacing.2.Under the condition of paragraph spacing is 60 cm,when the area constriction ratio ?₁=0.625,the cavitation number is the biggest and it is smallest when the area constriction ratio ?₃=0.375.The minimum cavitation number of three cases are 62.153,31.631 and 9.465.When the flow changes,the cavitation number of Q₁=20l/s condition is always the biggest,which is 58.451,and Q₃=30l/s condition is the minimum which is 18.034.Therefore,in the same case,the cavitation number gradually reduced with the increase of flow rate or the decrease of the area contraction ratio,at the same time,the ability of cavitation erosion resistance is abated and the probability of negative pressure and cavitation phenomenon is increasingly.3.Under the same condition of the area contraction ratio,the ability of pipe flow gradually reduces with the increase of paragraph spacing of two stage inner energy dissipation of tooth block,and the range is gradually slow and eventually stable.When the area contraction ratio ?₁=0.625,stable flow coefficient is close to 0.59,area contraction ratio ?₃=0.375,flow coefficient is close to 0.26.4.Under the same flow rate,the gap is obvious,when the area constriction ratio ?₁=0.625,the flow coefficient is the largest and when the area constriction ratio ?₃=0.375,the flow coefficient C is the minimum,which indicates that the capacity of pipe flow reduces with the decrease of flow area.5.In the same case,the effect of energy dissipation of pipe increases with the increase of paragraph spacing,and the range would be gradually slow.In 3plans,the larger the area contraction ratio,the most stable the energy dissipation effect.Compared 3 plans,it can be seen that when the area constriction ratio?₁=0.625,the dissipation increases nearly 7% in work of conditions Q₃=30l/s than Q₁=20l/s,and it is 38% when the area constriction ratio ?₃=0.375.It indicates that the effect of energy dissipation is more vulnerable by the impact of changing flow when the area contraction ratio is smaller with the rest of the conditions are the same.6.Under the same flow rate,the dissipation is the biggest when the area constriction ratio ?3=0.375 and its effect is the best,but it is opposite when the area constriction ratio ?1=0.625,which obviously shows that the energy dissipation effect is increasing with the decrease of the flow area.The trend of flow coefficient are the same in 3 plans,which are reduce with the increasing of paragraph spacing,and be close to stability after a certain distance.When the area constriction ratio ?1=0.625,the change is very small and when the area constriction ratio ?3=0.375,it is more obviously.So that the smaller the area contraction ratio is,the easier the dissipation changes with the increase paragraph spacing.7.The turbulent kinetic energy,turbulent kinetic energy dissipation rate and speed all have a significant boost and recover when water flows through tooth block,which suggests that the turbulence kinetic energy and its dissipation rateare related to the speed,and the higher speed is,the greater the turbulence kinetic energy is.The greater the dental paragraph spacing,the more obvious the flow energy dissipation effect is and the smaller the flow velocity in the second tooth block.The flow velocity is the largest in the center of the pipe axis and the less near the pipe wall.