Rayleigh-Benard convection in the presence of a weak lateral flow

Rayleigh-Benard convection has, for several decades, been used as a paradigm for the study of pattern forming systems. It has been particularly fruitful since the fluid dynamical equations which underlie the flow are well known and because it can be well controlled experimentally. It is now routine to control the geometry and temperatures to better than 0.1% which allows for good comparison to theory. When one adds a lateral flow, the system demonstrates characteristics of open flow systems. In a large range of flows and temperature differences the system becomes convectively unstable and exhibits extreme sensitivity to fluctuations in the fluid. These fluctuations drive the observed pattern. This work will present measurements of the noise which drives the observed convection rolls. The magnitude of the noise is consistent with thermal fluctuations. This is an example of microscopic Brownian motion generating the macroscopic patterns which develop in the system.