BENARD-MARANGONI INSTABILITY IN A VISCOELASTIC JEFFREYS FLUID LAYER

Coupled buoyancy (Benard) and thermocapillary (Marangoni) convection i n a thin fluid layer of a viscoelastic fluid are studied. The viscoela stic fluid is modeled by Jeffreys' constitutive equation. The lower su rface of the layer is in contact with a rigid heat-conducting plate wh ile its upper surface is subject to a temperature-dependent surface te nsion. The critical temperature difference between both boundaries cor responding to the onset of convection is calculated. The role of the v arious viscometric coefficients is discussed. In the appendix it is sh own that Jeffreys' constitutive relation is easily derived from thermo dynamic considerations based on extended irreversible thermodynamics.