For small values of the dimensionless viscosity parameter, namely α ∼< 0.1, the dynamics of non-radiating accretion flows is dominated by convection; convection strongly suppresses the accretion of matter onto the central object and transports a luminosity ∼ 10 − 10Ṁc from small to large radii in the flow. A fraction of this convective luminosity is likely to be radiated at large radii via ther...

Spherical (nonrotating) accretion flows with small-scale magnetic fields have been investigated using three-dimensional, time-dependent MHD simulations. These simulations have been designed to model high-resolution (quasi) steady accretion flows in a wedge computational domain that represents a small fraction of the full spherical domain. Subsonic and supersonic (super-fast-magnetosonic) accret...

Shear flows can form spontaneously in two-dimensional (2D) simulations of convection. These disperse convective plumes and decrease vertical transport. What is the physics these flows? Can they be avoided 2D? It was previously shown that increasing simulation aspect ratio prevent onset shear flows. With penetrative convection we explore a range ratios. We find small perturbations lead to format...

The solar convection zone exhibits a strong level of differential rotation, whereby the rotation period of the polar regions is about 25-30% longer than the equatorial regions. The Coriolis force associated with these zonal flows perpetually “pumps” the convection zone fluid, and maintains a quasi-steady circulation, poleward near the surface. What is the influence of this meridional circulatio...

Experiments study large-scale pattern formation during the growth of ammonium chloride (NH4Cl) from solution in a thin (Hele-Shaw) geometry. In particular a solid-liquid mixture ("mushy layer") forms in which growing solid NH4Cl crystals form a solid network interspersed with liquid. There are different ways that the mushy layer can be formed, however. If the cell is heated from below and coole...

Insect tracheal-respiratory systems achieve high fluxes and great dynamic range with low energy requirements and could be important models for bioengineers interested in developing microfluidic systems. Recent advances suggest that insect cardiorespiratory systems have functional valves that permit compartmentalization with segment-specific pressures and flows and that system anatomy allows reg...

Helioseismology has provided very detailed inferences about rotation of the solar interior. Within the convection zone the rotation rate roughly shares the latitudinal variation seen in the surface differential rotation. The transition to the nearly uniformly rotating radiative interior takes place in a narrow tachocline, which is likely important to the operation of the solar magnetic cycle. T...

In this paper, the problem of unsteady mixed convection boundary layer flow of a viscous incompressible fluid near the stagnation-point on a vertical permeable plate with both cases of prescribed wall temperature and prescribed wall heat flux is investigated numerically. Here, both assisting and opposing buoyancy forces are considered and studied. The non-linear coupled partial differential equ...