EFFECT OF INTERFACIAL DEFORMATION ON THE ONSET OF CONVECTIVE INSTABILITY IN A DOUBLY DIFFUSIVE FLUID LAYER

The effect of surface tension of a deformably free upper surface on th e onset of convective instability in a doubly diffusive fluid layer is investigated with the linear stability theory. The eigenvalue problem is numerically solved, employing the Runge-Kutta-Gill's method of ord er four and making use of the Broyden's method for correction of the s tarting values during the integration process. The results show that t he effect of Crispation number, C, becomes very sensitive on determini ng the possible mode of convective instability. The surface tensile an d thermosolutal modes can coexist stationarily at C = 8.44 x 10(-4). F or C < 8.16 x 10(-4), the whole system is dominated by the oscillatory mode. One of the interfacial effects, associated with the Bond number , Bo, do increase critical conditions of both stationary and oscillato ry modes. The Marangoni number, M, and the solutal Marangoni number, M (s), play important roles on causing the onset of the convective insta bility and, in turn, reinforce each other mutually.