What can thermal convection teach us about the nature of turbulence?
by: Professor Fritz Busse, University of Bayreuth
Thermal convection in a fluid layer heated from below provides a most convenient setting for experimental and theoretical studies of turbulence. The Rayleigh number R as a measure of the applied temperature difference is the control parameter. The Prandtl number is the second dimensionless parameter describing the ratio of the two nonlinearities governing the system. The evolution from simple convection rolls to convective turbulence with increasing R can either be simulated numerically or be studied through following sequences of subsequent bifurcations. The regular solutions obtained in the latter case often exhibit the patterns that become visible as coherent structures in the turbulent version of the system. Similarly, in experiments turbulence evolves usually with increasing control parameter through uncontrolled initial or inlet conditions. Alternatively, through controlled initial and boundary conditions sequences of subsequent regular spatially and time periodic flows may be realized as will be demonstrated by a short movie.
1.15 p.m. 10th May 2010 (4W 1.7, University of Bath).