Study On Numerical Simulation For 3-D Flow In Channel Bend

The natural river channel is composed by a series of bends and straight reaches. So, the study of the movement regulation of water in the bend with strong curvature is considered as the basis in the natural river and channel. The bend flow has lengthways flow added secondary flow becomes the spiral flow, which has complex 3-D characteristics together with its special geometry profile and boundary condition. If this kind of problem can be solved using numerical simulation, it not only can do some research on these flow structure and instruct the engineering, but also can save manpower, budget and time contrasting to the test. This paper has simulated the 180 degree bend flow using different turbulent models, which is provided by fluid computational software FLUENT and compare the results with experimental data to distinguish the dependability of numerical simulation qualitatively. The main contents and conclusions are as follows:(1) The movement phenomena and movement characteristics of water, the intensity of turbulent flow and the distribution of bed shear have been analyzed in detail from theory.(2) Numerical simulation of the three dimension flow in 180 degree duct has been simulated by using standard k -εturbulent model,R NG k -εturbulent model and Reynolds Stress turbulent mode respectively. VOF method is introduced to make tracks for free surface. The equations are segregated by using the Finite Volume Method (FVM) with the PISO algorithm adopted in the numerical program. The characteristics of bend flow by each turbulent model are obtained, including free water surface, velocity of lengthways flow, circulation flow, turbulent kinetic energy and turbulent dissipation and so on, and compare the results with experimental data.(3) Different distribution of the inlet velocity are adopted for the same turbulent model, such as constant distribution, index number distribution and logarithm distribution, and different results that are obtained have been compared. It shows that the model adopting logarithm distribution for inlet velocity is better to simulate the actuality.(4) The mesh lines are generated generally according to the direction of flow while simulating the flow. The simulation domain is divided into several regions in this paper and the different densities of meshes are employed to different regions. The meshes of key regions, such as curved conduits and the hydropneumatic interfaces are dense, while the meshes of secondary regions are sparse, which can control the amount of meshes effectively and improve the speed and precision of the simulation.The research work shows that standard k -εmodel can not effectively simulate the bend flow with strong curvature. Reynolds Stress model can successfully calculate the turbulent flow and the computational results are satisfactory. RNG k-εmodel is worse than Reynolds Stress model but have less calculation and need fewer computer time. With the development of the science and computer technique, as one strong tool to do research on flow structure in the channel bend, Reynolds Stress model will show the great superiority and then guide the engineering better.