Analysis Of Vortex Structure Evolution In Bionic Structure Surface Flow

Due to the discovery of coherent structures,turbulent drag reduction has opened a new wave of research,and exploring the intricate internal conditions can help enrich the theoretical system of drag reduction research and provide a certain theoretical basis for turbulent drag reduction.This paper uses Fluent software to study the evolution of the bionic structure boundary layer,study the evolution of the vortex structure,calculate the flow field of the grooved flat plate and the smooth plate,and explore the influence of the bionic groove structure on the turbulent boundary layer.Based on the lateral trench structure,this paper analyzes and explores the results of numerical simulation of LES based on Liutex parameters and Omega criteria.Firstly,the distribution law of Liutex vector is analyzed.The Liutex vector inside the trench is mainly dominated by the span component.The components in the x and y directions can be almost ignored.The existence of "rolling bearings" can be clearly shown in the cloud image.Among them,the vortex structure with the z-axis as the rotation axis is strong,and the lateral groove structure has a suppressing effect on the vortex structure.The effect is significant in the range below y + = 83,but its effect gradually decreases as the height increases.Secondly,the influence of grooves on turbulence parameters was explored.Inside the trench,there is a secondary vortex sweeping up and down and the lateral trench's own diversion effect.Studies have shown that its pulsating velocity in the spanwise direction is slightly `greater than the components in the other two directions.For the pulsating velocity,its diversion The effect is greater than the influence of the vortex core structure along the span in the trench.The turbulence intensity is dominated by the span direction and the flow direction is supplemented.The normal turbulence intensity is ignored.The Reynolds stress is small and the situation is relatively stable.On the side,the influence of the structure changes the watershed,and the turbulent intensity of the flow direction gradually takes the dominant position.This structure increases the turbulent intensity of the viscous bottom layer,and suppresses the turbulent intensity of the transition zone and the logarithmic layer.The overall effect is inhibitive,and the lateral velocity The suppression effect of the gradient in the transition layer is outstanding,but it is not ideal in the logarithmic layer.The overall values of Reynolds stress and Reynolds shear stress are smaller than those in the plate basin,but the effect of normal Reynolds stress is not very obvious.Then,the identification and comparative study of the vortex structure criterion were carried out.The adaptability of the Omega criterion to the research model was explored,and the change of the vortex intensity during the vortex evolution process was investigated using the Liutex parameter.In the smooth flat watershed,as the vertical height rises,the vortex intensity in the transition layer gradually increases,and the amplitude of the fluctuation increases,and the response is violent.The logarithmic layer goes vertically upward,and its law is exactly the opposite of the transition layer.The value gradually decreases,the amplitude of the fluctuation gradually increases,the vortex intensity gradually decreases,and the change is relatively gentle;in the trench watershed,the Liutex value in the immediately upper watershed increases sharply,so that the bottom has a certain vortex strength,and decreases.The strength of the vortex at the top is reduced,the growth rate is reduced,the activity of the transition layer is more stable,the amplitude of the logarithmic layer is smaller,and the stability of each layer of fluid is higher,which is beneficial to reducing the normal momentum exchange between fluids.The arrangement of part of the trench structure can reduce the watershed state on the upper side of the trench structure to a certain extent,so that the harmful effect of the structure on the watershed is reduced,and it has certain beneficial effects on the watershed on the rear side,but on the whole,the effect of the full trench layout is far from being achieved,and in some layouts,the influence of the mean value of Liutex-m and the fluctuation value are in the opposite state.The average value increases and then decreases with the increase of y+,and the fluctuation value With the increase of y+,it decreases first and then increases,and the trench structure has a better suppression effect on regions with higher vortex strength.