Laminar-Turbulent Transition in Radial Liquid-Film Flow on a Rotating Disk 4th Report, Linear Stability.

Abstract

The laminar flow in the radial liquid-film flow on a rotating disk has velocity profiles with a kind of three-dimensional boundary layer. The linear stability of the flow was analyzed, with the effects of Coriolis force and streamline curvature taken into account. In the experiment, the frequency of disturbance was detected through wall pressure and the direction of propagation of the spiral vortices was obtained by measuring the angle of distortion of the disturbance waves on the liquid surface. The results of the stability analysis showed that the instability of the flow changes, with an increase in the effect of disk rotation on the flow, from a viscous to an inflectional type : the weak three-dimensionality of the velocity profile causes a decrease in the amplification factor of disturbance, suppressing the transition accordingly, whereas the strong three-dimensionality promotes the transition because of the inflectional instability. The results of the stability analysis were in reasonably good agreement with the experimental results.