School Seminars and Colloquia

Convective methods of pumping and drag reduction

Applied Mathematics Student Seminar

by James D. Woodcock

Institution: The University of Melbourne
Date: Tue 9th October 2012
Time: 11:00 AM
Location: Botany - Turner Theatre

Abstract: It is the convection of the velocity field by itself that renders many
fluid mechanics problems mathematically challenging, and produces
complicated, and often non-intuitive flow phenomena. Pumping and drag
reduction are effectively related concepts, in that they both involve
increasing the volume flux of the fluid. Three different methods of
pumping and drag reduction have been studied, all of which result,
partially or entirely, from the effect of convection.

The first of these methods is the drag reduction obtained by the
addition of elastic polymers to a turbulently flowing liquid. This
effect is not well understood, and a complete physical explanation of
the phenomenon remains to be made. The second method is known as
"transpiration", and consists of a dynamic regime of blowing and
suction at the wall of the pipe or channel which imparts no net volume
flux upon the flow. The third method consists of oscillating waves
in the wall of the pipe or channel. This has particular relevance to
the valveless impedance pump, which consists of a thin tube, one
section of which is elastic and is subjected to rhythmic pinching at
some point offset from its centre. This pinching induces oscillating
waves within the wall of the tube, which in turn induce a flow.

These methods have been studied analytically, using techniques such as
perturbation analysis, which allow us to explore the physics at work
within the flow, and to infer the conditions under which the effect of
drag reduction may be maximised.

For More Information: Completion Seminar