Applied Math Seminar
Monday, November 1, 1999, 4:00pm, 120 Physics
Laurens E. Howle (Duke University, Mech Eng and Mat Sci Dept)
Boundary Effects in Controlled Rayleigh-Benard Convection
Abstract:- 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.
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