title: Spiral vortices and Taylor vortices in the annulus between rotating cylinders and the effect of an axial flow.
abstract: We present numerical simulations of vortices that appear via primary bifurcations out of the unstructured circular Couette flow in the Taylor-Couette system with counter rotating as well as with corotating cylinders. The full, time dependent Navier Stokes equations are solved with a combination of a finite difference and a Galerkin method for a fixed axial periodicity length of the vortex patterns and for a finite system of aspect ratio 12 with rigid nonrotating ends in a setup with radius ratio eta=0.5. Differences in structure, dynamics, symmetry properties, bifurcation, and stability behavior between spiral vortices with azimuthal wave numbers M=+/-1 and M=0 Taylor vortices are elucidated and compared in quantitative detail. Simulations in axially periodic systems and in finite systems with stationary rigid ends are compared with experimental spiral data. In a second part of the paper we determine how the above listed properties of the M=-1, 0, and 1 vortex structures are changed by an externally imposed axial through flow with Reynolds numbers in the range -40< or =Re< or =40. Among other things we investigate when left handed or right handed spirals or toroidally closed vortices are preferred.
authors.affiliation: Institut für Theoretische Physik, Universität des Saarlandes, D-66041 Saarbruecken, Germany.
authors.forename: Ch
authors.initials: Ch
authors.lastname: Hoffmann
authors.forename: M
authors.initials: M
authors.lastname: Lücke
authors.forename: A
authors.initials: A
authors.lastname: Pinter