| Chute Spillway is widely used in water conservancy construction as sluice structures to leak out the flood that planning capacity can not accommodate. There are many characteristics that these are large unti-width discharge,high flow velocity and energy concentration and if we don not dissipate the energy carried by the flow from Chute Spillway,it will damage the downstream buildings and environment a lot.The previous studies showed that Orifices Plate are arranged in Chute Spillway can obviously eliminate the water flow energy,reduce the flow velocity, and reduce the depth and length of stilling pool in order to minimize the project cost.The previous studies are based on the physical model experiment to get hydraulic parameters of measuring points through the measuring instrument. This method is simple,but the field data we can get is very limited. In addition, through the physical model experiment, we can only get finite kinds of working condition. As the development of computer technology and numerical model,people pay more and more attention to use mathematical models to simulate and calculate the complex flow phenomena and the internal structure of flow field.Considering these above factors,it studies flow field of Orifices Plate Chute Spillway by combining the physical model experiment and numerical simulation. This is rare in previous research on Orifices Plate Chute Spillway.This paper summarizes the five ralationships between energy dissipation rate and energy dissipation influence factors through the results of physical model experiment of Orifices Plate Chute Spillway.It designs 9 numerical simulation working conditions refering to the physical model experiment conditions.After getting the results of numerical simulation,it compares and analyzes the results between the numerical simulation and physical model experiment. At the same time, it discusses the different working conditions of water flow pattern and velocity distribution by the flow changing,the chute spillway slope changing and the number of orifices plate changing. In addition, it presents the flow field bottom pressure and turbulence intensity distribution of Orifices Plate Chute Spillway caused by energy dissipation influence factors changing which are not discussed in physical model experiment. The conclusions are as follows:1.Through analysis of the physical model experiment results of Orifices Plate Chute Spillway,it summarizes the five ralationships between energy dissipation ratio and energy dissipation influence factors increasing the chute spillway slope, the number of orifices plate and the orifices plate height can make the energy dissipation ratio risen.Increasing the chute spillway flow and the orifices plate hole area ratio can make the energy dissipation ratio declined.It shows the range of energy dissipation ratio caused by energy dissipation influence factors changing.From large to small is as follows:the flow(7.11%),the chute spillway slope(5.54%),the orifices plate height(4.01%), the number of orifices plate(1.92%),the orifices plate hole area ratio(1.44%).2.By Using software Fluent,it establishes 1:1 numerical model of the physical model experiment which has been done and gets the water flow pattern, distribution of the water surface and distribution of the flow velocity.The numerical simulation results fit the physical model experiment very well.That acts the use of RNGk-ε two equation turbulence model,two-phase flow VOF model and PISO algorithm for solving the discrete equations is feasible to simulate the flow field of Orifices Plate Chute Spillway.3.In order to explain that which turbulence model is much more accurate in this program,it compares standerd k - ε turbulence model and Realizable k - ε turbulence model to RNG k - ε turbulence model.The results show that the RNG k - ε turbulence model is more accurate in this program.From the angel of numerical simulation,it discusses the water flow pattern,the velocity distribution and,the bottom pressure distribution and the turbulence intensity distribution caused by the flow changing,the chute spillway slope changing and the number of orifices plate changing.The main conclusion is as follows:Water flow pattern distribution:(1)With the flow increasing, orifices plate makes adjustment effect on the Chute Spillway worse, the water flow pattern is more and more disorder, Gradually increasing the water surface.But export pattern and water surface of the three working conditions are basically stable;(2)With the slope increasing,orifices plate makes adjustment obviously effect on Chute Spillway;(3)With the number of orifices plate reduction, adjustment effect of the 4 stage on the flow is not as good as 5.Water flow velocity distribution:(1)With the flow increasing, distribution of the water flow velocity distribution rise gradually;(2)With the slope increasing, distribution of the water flow velocity distribution rise gradually;(3)With the number of orifices plate reduction, distribution of the water flow velocity distribution rise gradually between the each of orifices pate.Bottom pressure distribution:(1) With the flow increasing,the bottom pressure on the front of the first stage orifices plate increases from 0.5kpa to 2.4kpa.Between the first stage and the second stage of orifices plate,there is a relatively large impact zone of the bottom plate pressure.With the flow increasing,the impact zone gradually moves downstream;(2) With the chute spillway slope increasing,through the maximum bottom pressure is similar between 5% slope and 9.1% slope on the front of the first stage orifices plate,but the bottom pressure gradient between the each of orifices plate of the 9.1% slope is larger than 5% slope; (3) With the the number of orifices plate reduction,the region of the the maximum bottom pressure on the front of the first stage orifices plate becomes larger, at the same time the bottom pressure gradient between the each of orifices plate becomes larger too.Turbulence intensity distribution:(1) With the flow increasing from 5.1L/s to 15.3L/s, the pulsation of the flow field increases;(2) With the slope increasing, turbulence intensity distribution becomes larger. |
PDF Full Text Request