The Marangoni (surface-tension-induced) instability of surfactant-containing lenses of paraffin oil was investigated experimentally in the first part of this work. Results of these experiments are described and qualitative explanations are proposed. An unsuccessful attempt was made to quantitatively model a simple case of instability. / Attention was then shifted to the instability at a plane interface between two immiscible fluids, each containing a surface-active solute. The literature on this instability is reviewed and a simple finite-layer model is developed and subjected to a linear stability analysis. The mathematical structure and results of this analysis were used as tools in disclosing the physical mechanisms that underlie the onset of convective flow. It was found that the growth or decay of a normal-mode disturbance depends upon the relative rates of transport of momentum and solute in ways more subtle than have been recognized heretofore. In addition, the wave-number of the dominant mode was found to be determined primarily by the efficiency of solute transport, rather than by factors related to viscous dissipation. / The mathematical apparatus of the model was then used to elucidate the mechanism of conversion of chemical potential energy to kinetic energy. It was found that this connection cannot be made unless the surface excess concentration is explicitly included in the model. It is the convective transport of excess solute down chemical potential gradients in the interfacial plane that accounts for the conversion of chemical to kinetic energy. Use of the Gibbs adsorption equation allows this relation to be demonstrated quite simply. / The model was used in a global thermodynamic analysis to show that a convecting system does correspond to a process with less entropy production than a quiescent, diffusing system, at least for marginally supercritical values of the Marangoni number. This result follows because the generation of kinetic energy occurs at the expense of diffusive dissipation, while the net boundary fluxes are unchanged by convection. / A model for Marangoni instability at a cylindrical interface is developed in an Appendix. / Source: Dissertation Abstracts International, Volume: 44-02, Section: B, page: 0509. / Thesis (Ph.D.)--The Florida State University, 1983.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75065 |
| Contributors | IRVIN, BENJAMIN REID., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 165 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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