The Study On Characteristics And Control Measures Of Open Channel Flow With Large Diffusion Angle

In the actual project,limited by the lack of space,in the hole,canal combination often can not be arranged long enough open channel diffusion transition section,had to use large diffusion angle diffusion to achieve water convergence.However,in this kind of diffusion,due to the boundary conditions,the diffusion of water in the diffusion section is not sufficient,resulting in the uneven distribution of energy in the section,the separation of the boundary layer,the flow of the flow will appear when the mainstream shift A wide range of recirculation zones and whirlpools.This kind of bad flow will affect the normal use of the channel,which greatly limits the use conditions of the water distribution channel.In order to realize the smooth transition of the water flow in the diffusion section,it is necessary to understand the characteristics of the water flow and take effective control measures accordingly.In this paper,we try to study the flow characteristics and the control measures of the diffusion section through the series of hydraulic simulations.Based on the two diffusion section sink models,the characteristics of the hydraulic elements with the change of the flow and the diffusion angle and the diffusion of the water are studied.The hydraulic characteristics of the open channel are proposed to control the flow of the structure of the form,verify and optimize the potential of the triangular wing body control effect.In the case of no control measures in the open channel,the hydraulic factors such as water depth and flow velocity of the characteristic section of the diffusion section were measured.The flow pattern of the diffusion section and its connecting section was observed by applying tracer.The space of the hydraulic element The distribution of the boundary layer in the diffusion section,the energy loss of the water flow through the diffusion section,and the influence of the boundary condition on the flow pattern of the diffusion section and its connected section.It is found that when the diffusion angle is greater than 8 °,the flow is caused by the separation of the boundary layer.The vortex is relatively small,but the flow stability is poor,and the main flow is easy to produce random deviation.With the increase of the diffusion angle,the range and intensity of the flow backflow vortex are also increased.The distribution of the flow velocity of the characteristic section of the diffusion section is more uneven,the energy loss increases and the overcurrent capacity decreases.When the diffusion angle is increased to 45 °,the recirculation zone on both sides of the diffusion section produces strong shear squeezing to suppress the lateral diffusion of water flow,and also suppress the random deviation of the mainstream,and the instability of the flow is also inhibited.The overcurrent condition of the downstream section of the open channel diffusion flow has a certain response relationship with the flow state of the diffusion section,changing the overcurrent condition of the downstream section,the offset state of the mainstream section of the diffusion section and the shape of the return zone of the downstream connection section.According to the characteristics of open channel flow under the condition of large divergence angle,a submerged triangular wing body is proposed to control the flow pattern of large diffusion angle water flow.The diversion mechanism of this measure is studied.The experimental results show that the triangular wing body can reduce the horizontal distribution of the flow of water and enhance the stability of the flow structure of the diffusion section by strengthening the divergence movement of the water flow through the diversion of the water flow and the diversion of the two sides of the wing.When the flow through the diffusion section can be more evenly spread to the entire over-flow section,the diffusion section and its connection section of the flow is improved.