Study On The Influence Of Plate Vibration On The Flow Characteristics Of Near-Wall Flow Field

In the process of achieving lightweight of intelligent vehicle,the application of a large number of lightweight materials has changed the shape and material of the vehicle body panels,which obviously intensifies the complex vibration of the vehicle body surface when the vehicle is running,and makes the change of the flow field outside the vehicle more complex.At present,the traditional CFD simulation analysis regards the structure as a static rigid body,and takes the flow field as input to study the influence of the structure on the flow field.The simulation results are significantly different from the experimental results.In order to obtain reliable simulation results in the flow field simulation of intelligent vehicle,the traditional CFD simulation has obviously not been able to meet the requirements,so it is necessary to carry out an in-depth study of the influence of structural vibration on the flow field characteristics.It is difficult to get a regular conclusion if simulating directly the flow field of the body surface with random vibration.So it is necessary to separate the vibration of the structure and study the influence of the structure vibration on the flow characteristics of the flow field.In this paper,the body surface panels are simplified as a two-dimensional plate model,and the flow field around the two-dimensional vibrating plate is simulated and analyzed based on the lattice Boltzmann method.By adjusting the vibration form,amplitude and frequency of the plate to explore the influence of vibration on the flow characteristics near the wall.In order to solve the above problems,firstly,a two-dimensional simulation model of a stationary plate placed perpendicular to the incoming flow is established to analyze the aerodynamic characteristics and the flow field structure of the plate under different Reynolds numbers.And the results are compared with the literature to verify the reliability of the simulation method,which lays the foundation for the flow field simulation of the vibrating plate.At Re =300 the two-dimensional vibration model of a flat plate placed perpendicular to the incoming flow is simulated and analyzed.The vibration forms are shimmy around the center of mass and end point respectively.And the selected variables are frequency and amplitude.The given frequency is centered on the natural vortex shedding frequency and extends to both sides.The influence of frequency and amplitude on the aerodynamic characteristics and flow field characteristics of the flat plate are obtained: There is a lock-in region near the frequency ratio of 1,in which the vibration frequency of the plate resonates with the natural vortex shedding frequency,which has a greater impact on the lift force;The distribution of pressure and vortices in the locked region is symmetrical and uniform,while the structure of the lock-out region is asymmetric and complex.Comparing the two vibration forms,the resonance phenomenon is more obvious when shimmy around the center of mass;When it vibrates around the lower end,the lift coefficient matrix is no longer symmetrical about the origin due to the influence of the end effect.Considering that there are angles of attack in the structure of most panels on the vehicle body,the flow field of the plate with angle of attack is simulated at Re =300.The results show that compared with placing the plate perpendicular to the incoming flow,the flow field structure is more complex and the changes are more violently.The angle of attack accelerates the vortex shedding frequency of the plate and the lift direction is always along the negative direction of the y-axis.In terms of vibration,the existence of the angle of attack widens the range of the lock-in region,and the oscillation of the force coefficient is more intense.The location of vortex shedding at non fixed end has a tendency to move backward.Compared with placing the plate perpendicular to the incoming flow,the flow field structure is more complex,and the influence of vibration on the flow characteristics is more significant.The study results show that the plate vibration has a significant influence on the flow characteristics of the flow field near the wall.The lattice Boltzmann method used in this paper can solve the problem of vibrating flow around the structure well.The study has certain guiding significance for the numerical simulation of the flow field outside the intelligent vehicle.