SPIRAL VORTICES BETWEEN CONCENTRIC CYLINDERS

Spiral vortices appearing in Couette-Taylor flows are studied by means of numerical simulation. Transition curves from Couette to spiral vor tices for different radius ratios and wavenumbers have been calculated in order to test our technique. Critical Reynolds numbers, angular ve locities and slopes of the spirals at the onset of the instability agr ee with previous results [1], Non-linear solutions obtained by a pseud ospectral collocation method are studied, and they show a weak Det axi al flow. In order to counteract this effect, which is absent in the us ual experimental set-up, an axial pressure gradient has been included. This procedure has proved to be sufficient to make the axial flow neg ligible. The onset of a quasiperiodic flow for larger Reynolds numbers , corresponding to a secondary bifurcation is also presented.