Three-dimensional instabilities in the wake of a circular cylinder

The two- and three-dimensional wake structure behind a circular cylinder has been computed using a high-order spectral element technique. For the two-dimensional computations the predictions are compared with accurate experimental results and agree to within experimental uncertainty for the Strouhal number and base pressure coefficient. For the three-dimensional simulations, the two modes of three-dimensional instability, designated as modes A and B, both found experimentally but not previously computationally, have been captured. Mode A appears first at a Reynolds number slightly less than 200. As the Reynolds number is increased, there is a transfer of energy to mode B, which has a wavelength approximately one-fourth that of mode A.