### The onset of turbulence in pipe flow

- Series
- Math Physics Seminar
- Time
- Wednesday, September 19, 2012 - 15:00 for 1 hour (actually 50 minutes)
- Location
- Howey N110
- Speaker
- Dwight Barkley – Mathematics Institute, University of Warwick

**Please Note:** Host: Predrag Cvitanovic

More than 125 years ago Osborne Reynolds launched the quantitative
study of turbulent transition as he sought to understand the conditions
under
which fluid flowing through a pipe would be laminar or turbulent. Since
laminar and turbulent flow have vastly different drag laws, this question is
as important now as it was in Reynolds' day. Reynolds understood how one
should define "the real critical value'' for the fluid velocity beyond
which
turbulence can persist indefinitely. He also appreciated the difficulty in
obtaining this value. For years this critical Reynolds number, as we now
call
it, has been the subject of study, controversy, and uncertainty. Now, more
than a century after Reynolds pioneering work, we know that the onset of
turbulence in shear flows is properly understood as a statistical phase
transition. How turbulence first develops in these flows is more closely
related to the onset of an infectious disease than to, for example, the
onset
of oscillation in the flow past a body or the onset of motion in a fluid
layer
heated from below. Through the statistical analysis of large samples of
individual decay and proliferation events, we at last have an accurate
estimate of the real critical Reynolds number for the onset of turbulence in
pipe flow, and with it, an understanding of the nature of transitional
turbulence.
This work is joint with: K. Avila, D. Moxey, M. Avila, A. de Lozar, and B.
Hof.