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.