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DY: Fachverband Dynamik und Statistische Physik

DY 16: Fluid dynamics and turbulence II

DY 16.2: Vortrag

Mittwoch, 28. März 2012, 10:30–10:45, MA 144

Identifying Heat Transport Processes in Turbulent Rayleigh-Bénard Convection via a PDF Equation Approach — •Johannes Lülff¹, Richard J.A.M. Stevens², Michael Wilczek¹, Rudolf Friedrich¹, and Detlef Lohse² — ¹Institute for Theoretical Physics, University of Münster, Wilhelm-Klemm-Straße 9, 48149 Münster, Germany — ²Department of Science and Technology and J. M. Burgers Center for Fluid Dynamics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands

Rayleigh-Bénard convection, i.e. the convection of a fluid enclosed between two plates that is driven by a temperature gradient, is the idealized setup of a phenomenon ubiquitous in nature and technical applications. Of special interest for this system are the statistics of turbulent temperature fluctuations, which we are investigating for a fluid enclosed in a cylindrical vessel.

To this end, we derive an exact evolution equation for the probability density function (PDF) of temperature from first principles. Appearing unclosed terms are expressed as conditional averages of velocities and heat diffusion, which are estimated from direct numerical simulations.

Our theoretical framework allows to connect these statistical quantities to the dynamics of Rayleigh-Bénard convection, giving deeper insights into the temperature statistics and transport mechanisms in different regions of the fluid volume, i.e. in the boundary layers, the bulk and the sidewall regions.