The onset of three-dimensionality in an oscillating flow past a fixed circular cylinder

A computational study of the sinusoidally oscillating flow past a fixed circular cylinder has been performed to examine the viscous transition from 2D to 3D in the wake of the cylinder, i.e., the Honji instability. The primitive variables form of the Navier-Stokes equations was used with the discretization in the form of a combined finite-difference/spectral-method. Numerical results were obtained at a frequency parameter value of 196 and for a range of Keulegan-Carpenter (KC) numbers from 1 to 4. The calculations agreed quite well with experimental results. At KC = 1, the wake is 2D; spanwise structures begin to appear at KC = 2; separation has occurred by KC = 3.2; and the vortex structures have become chaotic by KC = 4. Calculated values of the feme coefficients also agree extremely well with the experimental values. Copyright (C) 1999 John Wiley & Sons, Ltd.