Structure of Complex Turbulent Shear Flow pp 175-184 | Cite as

# Interpretation of the Complex Turbulent Flow Generated by a Rotating Circular Cylinder

## Abstract

An experimental investigation of the wake generated behind a rotating cylinder has been carried out with the aid of hot-wire anemometry at a Reynolds number of approximately 10,000. Measurements have been made of Reynolds shear stresses and of the significant moments of streamwise and lateral velocity signals pertaining to several downstream stations and five cylinder peripheral velocities equal to 0.5, 1.0, 1.5, 2.0 and 2.5 times the free-stream velocity. In addition, correlation and spectral density functions of the velocity signals have been determined for selected locations within the flow. The moments show that, at any given station, as the peripheral velocity increases, the turbulence of the wake is damped and its characteristic width and mean velocity defect decrease. Moreover, displacements between the zero of the Reynolds stress and that of the lateral gradient of the mean streamwise velocity have been detected and, in some cases, the net turbulence kinetic energy production has been found to be negative. These findings are consistent with the correlation and spectral data obtained here, which establish the following: (i) for values of the ratio of peripheral velocity to free-stream velocity up to 1,0, a distinct Kármán vortex street exists in the near region of the wake; (ii) as this velocity ratio increases, the vortex street flow configuration is displaced with respect to the centre of the cylinder and its characteristic frequency, the Strouhal frequency, increases somewhat; and (iii) once the velocity ratio is much in excess of 1.0, Kármán vortex street activity ceases to exist, and hence, vortex shedding from the cylinder--which is a quasi-periodic process when this ratio is less than unity--becomes, in effect, a completely random phenomenon.

## Keywords

Streamwise Velocity Reynolds Shear Stress Vortex Street Lateral Velocity Turbulent Shear Flow## Preview

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