An Improved Approach to Conductive Boundary Conditions for the Rayleigh-Be´nard Instability

A technique is developed for predicting the stability limit of conductively coupled horizontal fluid layers heated from below and cooled above. The approach presented gives exact solutions of the stability problem and is numerically much simpler than previous multilayer solutions. Critical Rayleigh numbers are obtained for the case of three and four fluid layers separated by equally spaced identical midlayers of various thicknesses and conductivities with isothermal outer walls and for the symmetric two-layer problem with outer walls of finite thermal conductivity. Other configurations are considered briefly.