On the existence of a critical smear parameter for cellular vortex shedding from cylinders in nonuniform flow

The results of an experimental and numerical investigation into the existence of a critical shear parameter for cellular vortex shedding are presented. The experimental investigation of vortex shedding from a tapered cylinder in a linear shear flow reveals that vortex shedding is cellular, even when the shear in the flow is high. High shear parameters were achieved by orienting the tapered cylinder such that the shear in the flow added to the effect of the taper in the cylinder. Numerical simulations of the high shear experiment using a diffusive Van der Pol oscillator also indicate cellular shedding. The excellent qualitative and quantitative agreement between the numerical simulations and the experimental results validates a unique linear relationship between the shear parameter and a turbulent kinematic viscosity that scales the diffusive axial coupling term in the model. (C) 1998 Academic Press Limited.