Frictional Drag Reduction Provided with Small Bubbles in Concentric Rotating Cylinders

Drag reduction by compressible bubbles.

Drag reduction by bubbles in stationary turbulent flows is sensitive to the compressibility of the bubbles. Without this dynamical effect the bubbles only renormalize the fluid density and viscosity, an effect that by itself can only lead to a small percentage of drag reduction. We show in this paper that the dynamics of bubbles and their effect on the compressibility of the mixture can lead to...

Observations of the stratorotational instability in rotating concentric cylinders

We study the stability of density stratified flow between corotating vertical cylinders with rotation rates o < i and radius ratio ri/ro = 0.877, where subscripts o and i refer to the outer and inner cylinders. Just as in stellar and planetary accretion disks, the flow has rotation, anticyclonic shear, and a stabilizing density gradient parallel to the rotation axis. The primary instability of ...

Vortex suppression and drag reduction in the wake of counter-rotating cylinders

The flow over a pair of counter-rotating cylinders is investigated numerically and experimentally. It is demonstrated that it is possible to suppress unsteady vortex shedding for gap sizes from one to five cylinder diameters, at Reynolds numbers from 100 to 200, expanding on the more limited work by Chan & Jameson (Intl J. Numer. Meth. Fluids, vol. 63, 2010, p. 22). The degree of unsteady wake ...

Magnetohydrodynamic Flow in Horizontal Concentric Cylinders

This article presents the exact solutions of the velocity and temperature fields for a steady fully developed magnetohydrodynamic flow of a viscous incompressible and electrically conducting fluid between two horizontal concentric cylinders. Our study focuses on the influence of the Hartmann number, Brinkman number, Péclet number and inner radius on the fluid temperature field, entropy generati...

Simulations of Turbulent Drag Reduction Using Micro-Bubbles