Fluid Engineering Laboratory
Department of Mechanical Engineering
Meiji University


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Wake behind a Circular Cylinder


Measurements of three-components of velocity and vorticity of cylinder wake have been carried out by using stereo-PIV method. A cylinder having 15mm in diameter and 200mm in axial length was placed in a uniform flow created by a low turbulence water channel. Temporal series of 2D-3C velocity distributions were obtained by using stereo-PIV method, and 3D vorticity iso-surfaces were successfully reconstructed by assuming Taylor's frozen hypothesis based on the convection velocity determined by the mean flow. Visualization of the vorticity field in three-dimensions reveals spatial evolutions of Karman's vortex street and rib structures connecting successive vortices. Vortex structure having the different sign of the streamwise vorticity in the successive shear layer with spanwise wave length of approximately 4 times of cylinder diameter was observed at Re=200. This was an experimental evidence of the mode A pattern observed by others. At Re=1000, flow becomes more complicated and structures were broken into turbulence.



Perspective view

Side view

Top view

Re=200, x/D=2




Perspective view

Side view

Top view

Re=200, x/D=4


Green:spanwise vorticity component, Red and Blue:Positive and negative sign of root-sum-squared streamwise and transvers component of the vorticity. Direction of the mean flow is left to right.



Perspective view

Side view

Top view

Re=1000, x/D=4


Green:spanwise vorticity component, Red and Blue:Positive and negative sign of root-sum-squared streamwise and transvers component of the vorticity. Direction of the mean flow is left to right.