Study On The Simulation Technique And Stable Geometry Of Vegetated River

Along with the deteriorating of ecological environment, the increasing of people's environmental awareness and the Sustainable Development Strategy, constructing being put forward, ecological river is attracting more and more attention. The development of ecological river not only functions the basic effect of flood passage, but also has the environmental protection and beautifying the landscape effects.Through methods like physical model experiments, theoretical analysis and numerical simulation which are used to do the corresponding study work, this thesis is aimed to reveal the effects of plant community to the fluid in the vegetated river, root system influeces, sediment motion discipline and hydraulic geometry adjustment. Meanwhile, the predecessor's thread of vegetated river is expanded.Physical model experiments are aimed to study the effects of plant root system to the soil erosion resistance at the bank slope in the vegetated river. The experiments choose three kinds of natural plants like ophiopogonjaponicus, reed and wormwood. Experimental parameters of fluid, topography, root system pattern and erosion quantity are measured through the experiments. The result shows that the more developed of root system, larger of the maximum root area ratio (RAR) value and deeper the root can reach, the more effects it will take on the bank protection and wider range it will affect. The erosion resisting ability of the soil body is enhanced by the reasons above. A general formula about depth distribution of the root system is obtained at the same time.In order to reveal the nature of the experimental phenomena mentioned above, an expression of root system acting force is proposed. By using relevant theories, the paper derives the incipient velocity of sediment at the bank slope, sediment transportation discipline and the adjustment of bank slope topography. Each of them has an expression considering the root acting force factor. According to the incipient velocity, critical bank slope is proposed; its expression is derived at the same time. Then the methods of determining the root force factor is investigated, the relationship between root force factor and RAR is given.With the help of numerical methods of finite difference method (FDM) and fourth order Runge-Kutta method, the paper uses the MATLAB language to program and solve the theoretical problems studies above. By comparing with the experiments'data, theoretical derivation is verified. The result of critical bank slope solving shows a preform of the channel section tending to steady.The introduction of Shannon's entropy theory gives another way to explain the discipline of river bed evolution except from the method of mechanism based theories. By using this method, hydraulic geometry adjustment formula considering RAR is derived. The formula is verified by the physical model experiments.The thesis also uses the commercial fluid analysis software of FLUENT to build simple three dimensional vegetated river channel models and tentatively simulate the effects of plant community to the flow. Simulation is taken under two conditions of emerged and submerged. The simulation result shows that under the submerged condition, the phenomenon of fluid at the bank flowing back to the main channel is more prominent, the intensity and range of the turbulence are larger than that under the merged condition.