We consider the local convective and absolute instabilities of the boundary layer on a rotating sphere located in a uniform axial flow, extending our previous work, which considered still outer fluid. Axial flow is seen to stabilise the convective instabilities, and our predicted onset of the spiral vortices is in good agreement with existing experimental data. The vortex angle is found to incr...

Abstract

We investigate dynamical interactions between turbulent convection and g-mode pulsations in ZZ Ceti variables (DAVs). Since our understanding of turbulence is rudimentary, we are compelled to settle for order of magnitude results. A key feature of these interactions is that convective response times are much shorter than pulsation periods. Thus the dynamical interactions enforce near uniform ho...

We consider the effect of mass flux through the lower boundary of the general class of rotating BEK boundary-layer flows. This class includes the Bödewadt, Ekman and von Kármán flows as particular cases. A theoretical study is presented which considers the onset of convective instability modes (both stationary and travelling relative to the rotating system) and local absolute instability. Sucti...

We investigate dynamical interactions between turbulent convection and g-mode pulsations in ZZ Ceti variables. Since our understanding of turbulence is rudimentary, we are compelled to settle for order-ofmagnitude results. A key feature of these interactions is that convective response times are much shorter than pulsation periods. Thus the dynamical interactions enforce near uniform horizontal...

To be a formation mechanism of such large-scale structures as giant molecular clouds (GMCs) and HI superclouds, the classical Parker instability driven by external gravity has to overcome three major obstacles: The convective motion accompanying the instability generates thin sheets than large condensations. The degree of density enhancement achieved by the instability is too low to make dense ...

We report an experimental study of the secondary modulational instability of a one-dimensional nonlinear traveling wave in a long bounded channel. Two qualitatively different instability regimes involving fronts of spatiotemporal defects are linked to the convective and absolute nature of the instability. Both transitions appear to be subcritical. The spatiotemporal defects control the global m...