Thermal stability of two horizontal fluid layers with radiative heating from above: application to pool fires supported by water

The thermal stability of a two fluid system, with thermal radiative heating from above, has been considered. The upper fluid layer is treated as a participating media while thermal radiative effects are considered negligible in the lower fluid layer. The contribution of thermal radiative heat transfer is included in the formulation using a Milne-Eddington approximation. A qualitative measure of the spectral behavior of radiative transfer is obtained in the specification of the Planck and Roseland mean absorption coefficients. The governing equations and boundary conditions are approximated by truncated Chebyshev series. The main conclusion of this investigation is the discovery that thermal radiation is not responsible for the initial instability, as has previously been proposed. Results indicate that the initial instability is due to surface tension gradients, i.e. a Marangoni instability.