Numerical Simulation Of Taylor-Couette Vortex Flow Based On Large Eddy Simulation

The transient numerical simulation of Taylor-Couette wavy eddy current field is carried out by large eddy simulation(LES).According to the velocity vector field information of the flow field on the meridian plane of the annulus at different times obtained by simulation,theΩ vortex identification method is used to obtain the vortex and vortex core distribution cloud map on the meridian plane of the annulus at each time,and then Image-Pro Plus 6.0 is used for image recognition processing to obtain the vortex and vortex core area,periodic change time and other periodic laws.The periodic change process of Taylor-Couette wavy vortex field is studied from two-dimensional and three-dimensional perspectives.By selecting the characteristic line,the characteristics of the velocity and the velocity fluctuation span in different regions are analyzed.Finally,the fluctuation characteristics of Taylor-Couette wavy eddy current field are comprehensively analyzed from two-dimensional and three-dimensional perspectives.The main conclusions of this paper are :1.In Taylor-Couette wavy vortex field,the velocity vector field and the distribution of vortex and vortex core in the meridional plane of the annulus have periodic laws.The size and shape of adjacent vortex and vortex core change periodically.The position of the vortex center vibrates and drifts in the vertical and horizontal directions,and the flow direction of the mainstream liquid between the vortex pairs changes periodically.2.When Re is 488,586,732,878,976,1220,1366,1464,1708 and 1952,the vortex cycle time is 12.94 s,10.99 s,8.88 s,7.59 s,6.80 s,5.47 s,4.34 s,1.93 s,1.68 s and 1.49 s,and the vortex core cycle time is 12.50 s,10.83 s,9.00 s,7.47 s,6.83 s,5.49 s,4.34 s,1.91 s,1.69 s and1.50 s.3.In the Taylor-Couette wavy vortex field,the change period of the area of the vortex and the vortex core is almost the same.The vortex and the vortex core are integrated.The vortex core,as the strength core in the vortex,is dominant in the periodic change.The change trend of the vortex can be predicted by the change trend of the vortex core.4.The period of Taylor-Couette wavy vortex gradually decreases with the increase of rotational Reynolds number,indicating that the numerical change of the period can reflect and measure the transformation process of Taylor-Couette vortex field shape to a certain extent.5.The three-dimensional vortex fluctuation phenomenon of Taylor-Couette wavy vortex field is obvious and has periodic characteristics : at low speed,the vortex fluctuation in the flow field is large and the fluctuation period is long;at high speed,the fluctuation amplitude is greatly reduced,the fluctuation period is shortened,the contact area of the adjacent vortex surface becomes larger,and the phenomenon of vortex pair fusion and separation occurs.6.In a cycle,Taylor-Couette wavy eddy current field annulus meridian plane on the characteristic line of the radial velocity variation characteristics are as follows : the axial velocity direction changes twice,and the direction of the cycle is consistent;the radial velocity direction remains unchanged,and the two characteristic lines are opposite;the tangential velocity remains unchanged,which is the rotation direction of the inner cylinder.7.The velocity fluctuation span of each region on the characteristic line of the annular meridian plane increases with the increase of the inner cylinder speed.The axial direction is the most intense fluctuation in the inner wall area of the vortex pair,the most intense fluctuation in the outer wall area between the vortex pairs,and the opposite in the tangential direction.In the radial direction,the fluctuation near the outer wall between the vortex pairs is the most intense,and the position of the inner wall of the vortex pair has no effect on the fluctuation.The velocity fluctuation of the fluid between the vortex pairs is more intense than that in the vortex pairs.8.The region with violent velocity fluctuation on the meridian plane of two-dimensional annulus is the separation region of adjacent vortex flow trajectories;in the three-dimensional space,the inter-vortex fluid flows upward or downward around the vortex during the period,and the fluid micro-clusters rotate spirally around the inner cylinder,jumping up and down,prompting the vortex center to move up and down continuously,and promoting the mainstream liquid to flow back and forth periodically.