Experimental Investigations On The Fluid Flow Between Two Coaxial Rotating Conical Cylinders

The coaxial rotating conical cylinders is an extensive study of the classic coaxial rotating cylinder problem.Because the centrifugal force of the coaxial rotating conical cylinders changes with respect to the radius,the flow field in the annular space exhibit a complex three-dimensional character.The research use flow visualization and the PIV experiment to qualitatively and quantitatively analyze the flow field in the annulus gap between coaxial rotating conical cylinders,discussing the influences of rotational speed and gap width under the positive and reverse conical cylinders equipment,systematically studying the cyclic variations of spiral vortex,velocity and vorticity variations,spiral vortex cycle,mean flow field distribution,and Reynolds stress distribution of coaxial rotating conical cylinders.The experimental results show that the periodicity of spiral vortices is different between the positive and reverse conical cylinders.Under the positive conical cylinders,the positive vortex dominates the annulus,the position of the first vortex is relatively fixed and the second vortex changes periodically,beneath it,the new vortex pair will continue to be generated as the cycle repeat,and the vortex pairs in the annulus will move upwards gradually.While under the reverse conical cylinders,the negative vortex dominates the annulus,and the first vortex changes periodically,above it,the new vortex pair will be constantly generated as the cycle repeat,and the vortex pair will gradually move downwards.There are similar points in the radial velocity and vorticity distribution,spiral vortex cycle and the Reynolds stress distribution between the positive and reverse conical cylinders.The radial velocity and vorticity of the fluid alternately change positively or negatively with the height.When the radial velocity alternates positively or negatively,positive and negative vortices are formed in the annulus.The zero point of radial velocity corresponds to the extreme point of the vorticity,while the zero point of vorticity also corresponds to the extreme point of the radial velocity.When the gap width is constant,the total cycle time of the vortex movement within the annulus will decrease as the inner cylinder rotation speed increases,and the number of vortices in the annulus remains basically unchanged.When the rotational speed of the inner cylinder is constant,the total cycle time of the vortex movement in the annulus increases as the gap width increases,and the number of vortices in the annulus decreases accordingly.At different gap widths and inner cylinder rotation speeds,Reynolds stress is dominated by Reynolds radial normal stress.Reynolds radial normal stress is mainly concentrated in the middle of the annular gap,and Reynolds axial normal stress is mainly distributed in the annular gap near the wall surface.