Fluid-solid Coupling Numerical Simulation Of Variable Diameter Pipe Under The Periodic Vibration

The spiral flow of the variable diameter tube is widely used in fluid equipment such as cyclone separators,centrifugal equipment and rotating machinery.During the operation of these equipments,they are often subjected to internal or external fluid disturbances,and the coupling effect of vibration conditions on fluid and structure,will cause the flow field evolution and structure of the movement.At present,under the action of fluid-solid coupling,some valuable results have been made in the safe operation and reliable design of the structure.But the effect of fluid-solid coupling on the spiral flow field in the variable-diameter tube under periodic vibration,the temporal and spatial evolution of the flow field during a vibration period,and the relationship between the structure motion and the flow field are still relatively few.In this paper,the spiral flow and the structural motion characteristics of the variable-diameter tube under periodic vibration are studied.Based on the flow characteristics of the spiral flow of the variable diameter tube,the fluid domain calculation model is established,and the control equation is closed by RSM turbulence model.A solid domain computational model is established and the Newmark numerical integration method is used to solve the structural dynamic equations.The fluid-solid coupling model of the variable-diameter tube under the vibration coupling condition is established by using the iterative weak coupling method and dynamic mesh technology,the coupling interface exchanges data by interpolation.The numerical calculation method and the calculation parameters are optimized.The acceleration of the variable-diameter tube under periodic vibration is experimentally tested,and the reliability of the model is verified by comparing the experimental results with the fluid structure interaction.Based on the above calculation method,the fluid-solid coupling calculation is carried out for the periodic vibration variable-diameter tube.The velocity variation law and the spatiotemporal evolution of the fluid in a vibration cycle,the corresponding structural motion characteristics and time-course response changes are studied.The results show that the period of fluid vibration is consistent with the excitation force,but there is phase deviation.Axial velocity,tangential velocity and radial velocity are affected by the motion of the structure,but the coupling action makes the velocity values difference between the structure and the flow field,and the three directional velocities affect each other.The motion trajectory of the structure is irregular "O" type,the vibration form is parabolic.The study of the vibration frequency is the same and the excitation force is different,results shows that with the increase of exciting force,the motion amplitude of convection field and structure increase,but the law is similar.The condition with same exciting force,different vibration frequency and resonance was conducted firstly.The results showed that along the direction of the exciting force,velocity of 3direction swung positively or negatively with the movement of structure,the FSI effect made the offset of speed less than the offset of structure.We could get different vibration frequency under different oscillating amplitudes,in which the oscillating amplitude under high frequency is small,and the biggest swing occurred along with resonance.The axial velocity to the bottom flow trend increased on the vertical vibration direction,and the tangential velocity was asymmetry while radial velocity increased significantly under different excitation frequencies.The deformation of the structure was different with different deflection angle of trajectory.Different deflection angle of trajectory could cause different of the flow field distribution on each section.In this paper,the flow characteristics and the motion of the helical flow in the circular vibration tube are studied.The displacement,time-history response and the interaction of the internal fluid are obtained under different excitation force,different excitation frequency and resonance condition.The influence of the internal flow field characteristics can provide theoretical guidance for the application of the spiral pipe with variable diameter tube under the vibration condition.