# Laurens E. Howle : Boundary Effects in Controlled Rayleigh-Benard Convection

We investigate the effect of finite horizontal boundary properties on the critical Rayleigh and wave numbers for controlled Rayleigh-Benard convection in an infinite horizontal domain. Specifically, we examine boundary thickness, thermal diffusivity and thermal conductivity. Our control method is through perturbation of the lower boundary heat flux. A linear differential-proportional control law uses the local amplitude of a shadowgraph to actively distribute the lower boundary heat flux. Realistic boundary conditions for laboratory experiments are selected. Through linear stability analysis and experiment we examine the important boundary properties and make predictions of the properties necessary for successful control experiments. A surprising finding of this work is that for certain realistic parameter ranges, one may find an isola to time-dependent convection as the primary bifurcation.

**Category**: Applied Math and Analysis**Duration**: 01:04:51**Date**: November 1, 1999 at 4:00 PM**Views**: 25-
**Tags:**seminar, Applied Math Seminar

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