Experimental study for multi-scale vortex structure around a rotating circular cylinder in the stratified fluid and the measurement of fluctuating wall shear stress by electro-chemical method

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An experimental study has conducted to understand the relationship between multi-scale vortex structures developed around a rotating circular stratified flow and the fluctuating wall shear stress. In order to examine the validity of the electro-chemical method for wall shear stress, preliminary experiments were achieved in the pipe flow, circular Couette flow, and flow around a circular cylinder at rest. As the results, electro-chemical method had not established satisfactory, because fluctuating wall shear stress contains unsolved noise. The flow induced by impulsively rotating circular cylinder, rolls up the mushroom-type vortex ring array, and the evolution of the vortices lead to subsequent large-scale layered formation, i.e. multi-scale vortex structure. During the layered formation and the rearrangement of the vortices, the flow exhibits oscillating motion. Those typical spatial and temporal scales of velocity and density field were extracted.