Hydrodynamic stability of viscous flow between rotating porous cylinders with radial flow

A linear stability analysis has been carried out for flow between porous concentric cylinders when radial flow is present. Several radius ratios with corotating and counter-rotating cylinders were considered. The radial Reynolds number, based on the radial velocity at the inner cylinder and the inner radius, was varied from -30 to 30. The stability equations form an eigenvalue problem that was solved using a numerical technique based on the Runge-Kutta method combined with a shooting procedure. The results reveal that the critical Taylor number at which Taylor vortices first appear decreases and then increases as the radial Reynolds number becomes more positive. The critical Taylor number increases as the radial Reynolds number becomes more negative. Thus, radially inward flow and strong outward flow have a stabilizing effect, while weak outward flow has a destabilizing effect on the Taylor vortex instability. Profiles of the relative amplitude of the perturbed velocities show that radially inward flow shifts the Taylor vortices toward the inner cylinder, while radially outward flow shifts the Taylor vortices toward the outer cylinder. The shift increases with the magnitude of the radial Reynolds number and as the annular gap widens.