Influence of the geometry on the structure of the flow between a pair of corotating disks

Constant-property laminar flow in the space between two coaxial disks corotating in a fixed cylindrical enclosure is investigated numerically over the Reynolds number range 0 less than or equal to Re less than or equal to 82 380 for interdisk spacing to disk radius aspect ratios in the range 0.05 less than or equal to S less than or equal to 0.20. Most of the 3D calculations correspond to regions in the (Re, S) map slightly above the 2D-3D transition, where the 2D (axisymmetric) steady flow can bifurcate into two different families of unsteady 3D flow; (a) at sufficiently large values of S or Re, into a flow that is asymmetric with respect to the interdisk midplane; (b) at intermediate values of S and Re, into a flow that displays shift-and-reflect symmetry with respect to the interdisk midplane. Qualitative and quantitative comparisons with previous experimental and numerical results are established. The structure of the 3D flow is analyzed as well as the jumps in wave frequency when it experiences a change in its circumferential wave length. It is shown that each family of 3D flows is characterized by a distinct behavior in the frequency/wave length transitions. Present calculations and analysis provide the necessary additional evidence about the duality of this class of flows to reinterpret the numerical and experimental results previously reported by Humphrey ef al. [Phys. Fluids 7, 1225 (1995)] and Abrahamson ct al. [Phys. Fluids A 1, 241 (1989)]. (C) 1999 American Institute of Physics. [S1070-6631(99)01401-4].