Experimental Study On Taylor-Couette Flow Under Non-Uniform Rotation

The Taylor-Couette flow model is an ideal model for conducting experiments.It has a simple geometric structure and a variety of flow regime changes.The study of Taylor-Couette flow has lasted for a hundred years.It not only has great theoretical research value,but also has great application space,such as liquid-floating rotor micro-gyroscopes,bioreactors and optimization of the anticoagulant reactors.At present,most of the research on Taylor-Couette flow is focused on the condition of uniform rotation,and the research on non-uniform rotation is relatively lacking.In this paper,in order to deeply study the characteristic changes of Taylor-Couette flow under non-uniform rotation conditions,an experimental device suitable for non-uniform rotation conditions is designed and experimentally studied.The specific results are as follows:The formation of vortices and the disappearance of vortices in the process of rotation were observed through flow display experiments,and the changes of vortex morphology at each stage were recorded.In terms of vortex generation,it is found that when the volume of individual vortices in the annular gap is large,new vortices will be generated on the wall surface close to the inner cylinder.After a period of time,the newly generated vortices will make the volume of the vortices in the annulus close to the same.The morphological changes of vortices under non-uniform rotation are observed by PIV technology,and it is found that each vortex in the annular gap will generate a small depression near the wall surface of the inner cylinder during the acceleration process.The depression gradually increases with the rotation of the vortex center,creating a semi-heart-shaped gap at one side of the vortex.The gap lasts for a short time,and then the tail tip of the gap will combine with the head of the gap to restore a complete vortex.In the process of combining the tail tip with the head of the vortex gap,the liquid at the original position of the vortex core will be re-fused with the liquid outside the vortex core.During the deceleration process,a new vortex is born in the form of a tip in the area near the junction of the positive vortex and the negative vortex below the inner cylinder wall,where the maximum radial velocity in the outward direction exists,and the position of the tip birth also determines each a pair of vortices will have a tip to appear.The newly born vortex does not form,but merges with the positive or negative vortex with the fluctuation in the annular gap until each vortex returns to a relatively static state.During the acceleration process,the vortex shape changes little,and it is a laminar vortex.The shape of the vortex changes greatly during deceleration,showing a wave vortex.Regarding the change of the speed in the annular gap under the condition of non-uniform rotation,during the acceleration process,the acceleration of the rotation speed of the inner cylinder will increase the overall radial speed in the annular gap,but no obvious change rule has been observed.During the deceleration process,the speed in the annulus decreases as a whole,but the fluctuation decreases,that is,it decreases as a whole but increases at a certain moment,typical characteristics of wavy vortices.The positive vortex decreases faster in the radial velocity,and the negative vortex decreases very slowly in the radial velocity.