STABILITY OF THE FLOW AROUND A CYLINDER - THE SPIN-UP PROBLEM

In this paper the evolution of vortical disturbances within a boundary layer occurring at a circular cylinder is discussed. As the body starts to spin around its generator a temporally growing layer results and the underlying centrifugal nature of this system allows Taylor-Gortler vortices to develop. The initiation of these modes is caused by axially symmetric wall imperfections, and so this constitutes a receptivity problem. For vortices of order one wavenumber a vortex wedge is formed and the final structure of this mode is determined by a right-hand branch calculation. The inviscid limit of the calculation is also discussed and this may well be relevant to modes with order one wavenumber introduced after the layer has partially evolved.