Study On Hydraulic Characteristics Of Wake Stream Of Permeable Tetrahedron(s) And Application

Based on the experimental research and theoretical analysis, this paper utilized modern measuring and testing techniques for fluid to study in detail the wake stream characteristic of permeable tetrahedron and its group effect, and the main innovations and achievements of this study could be summarized as follows:1, In the aspect of PIV technique: A expressions of interrogation window is established, and the size of the window is diminished from four times of maximum particle movement displacement to there times. Based on the expressions, the search path of correlation analysis is improved by reducing the search area of correlation analysis, and not only analysis calculation and analysis time are reduced greatly, but also the accuracy and the reliability of correlation analysis is improved effectively. Utilizing multi-evidence reasoning to identify and remove miss-vector is brought up for the first time, and the multi-evidence reasoning Hopfield neural network model for removing miss-vector is established. The effect of velocity gradient to vector identification accuracy is researched, and the effect can be eliminated by adjusting the sample distance of correlation analysis. The selection of object neural cell in the network model is defined in theory. And the superiority of the above methods is proved by systemic experiment.2, In the aspect of wake stream characteristic of permeable tetrahedron Permeable tetrahedron wake stream take 0.8 Ho as the critical field height, then the flow velocity and the turbulent characteristic of the wake stream whose field height is above 0.8H₀ is visibly different from the flow velocity and the turbulent character of the wake stream whose field height is below 0.8H₀. The effect mechanism of permeable tetrahedron to the speed reduction and the silt promoting of wake stream field is opened out. After putting in permeabletetrahedron, the speed reduction area length of wake stream field exceeds 3.5 /0 inrang of 0.8 H₀ and Z direction flow velocity is slower, then it is very helpful for mud sediment. The research indicates that the speed reduction effect of squareness section permeable tetrahedron is better than that of rotundity section permeable tetrahedron, so squareness section permeable tetrahedron is commended in practical application.3, In the aspect of hydraulic characteristic and optimization design ofpermeable tetrahedrons?The consanguineous relation between the resistance characteristic ofpermeable tetrahedrons to stream movement and the relative height y^ ofpermeable tetrahedrons and the turbulent characteristic change of permeable tetrahedron wake stream in colony domino offect are opened out.?To be directed against the existent permeable tetrahedrons problem in project application, the optimization design scheme of permeable tetrahedrons application is brought forward:A > The speed reduction effect of the overhead ratio s and the pole's length-width ratio X of permeable tetrahedrons to permeable tetrahedrons wake stream is visible, then when ï¿¡ = 4.8 and i = 16 permeable tetrahedrons have nicer speed reduction effect.B> As the permeable tetrahedrons casting length is controlled about 20m, the project devotion can be kept economical and reasonable comparatively.C> The effect height of wake stream speed reduction area is in the rangeof0.8/f0. The effect of the permeable tetrahedrons casting height to wake streamspeed reduction area is mostly incarnated as the height range increase of speed reduction area.Dx On condition that permeable tetrahedrons is not effected from another wall, the speed reduction effect width of permeable tetrahedrons to the water at the bottom of far off wall outside is about \.2².6H (calculate from frame outside).? The effect of bend top rush stream to the speed reduction effect and range of permeable tetrahedrons is opened out. For the small angle bend (<20°), top rush stream has not visible effect to the speed reduction effect of permeable tetrahedrons, and the speed reduction ratio is close to that of straight riverway, then the design parameter can refer to the production of straight riverway. However, for the big angle bend (>20°), it is better to choose the whole-bank protection.