FLOW REGIMES AND VORTEX COMPETITION IN MODIFIED TAYLOR COUETTE SYSTEM: INNER ROTATING WAVY CYLINDER COAXIAL WITH A SMOOTH STATIONARY OUTER CYLINDER

The hydrodynamic instability of a viscous fluid flow in an annular space between a rotating inner cylinder having axi-symmetric wavy (cosinusoidal) surface, coaxial with an outer fixed smooth cylinder is studied both numerically and experimentally. The basic flow is two-dimension al, axi-symmetric with two counter-rotating vortices per wavelength. On one hand, a CFD code based on a finite volume technique (FLUENT) is used for flow simulations and on the other hand, the Particle Image Velocimetry (PIV) and wall shear probe measurement techniques are used, to localise the transitions and to understand the competition between Taylor's vortices and those imposed by the wavy surface. In this flow system, different flow regimes (steady and transient states) appear which are not characteristics of the flow in right circular cylinders geometry. The Taylor vortices appearing in the modified system have to compete with the vortices forced by the geometry.