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 cir cular 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 primit ive variables form of the Navier-Stokes equations was used with the discret ization in the form of a combined finite-difference/spectral-method. Numeri cal results were obtained at a frequency parameter value of 196 and for a r ange of Keulegan-Carpenter (KC) numbers from 1 to 4. The calculations agree d 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 v alues. Copyright (C) 1999 John Wiley & Sons, Ltd.