Dynamics and Instability Mechanisms of Single and Double Layered Fluid Flowmodels

Abstract

The thesis covers the dynamics and instability mechanisms of single and double-layered fluid newlineflow down a variety of bottom structures originating from many natural, technological, and newlineindustrial applications. Both numerical and analytical approaches are implemented to solve the newlinegoverning equations that couple mass conservation and the unsteady, two-dimensional Navier- newlineStokes equations. The generation of waves through the surface instability in single or doublelayered newlinefilm or the interfacial waves between two immiscible fluids drastically degrades the quality newlineof the final coated surface and deteriorates the quality of the manufacturing of photographic newlinefilms in different technological applications. That s why understanding the physical mechanism newlineof such instability problems and providing different strategies for controlling these instabilities newlineseems to be attracting more attention in the thesis. The following are some active and passive newlineways to control disrupted modes in the flow system: (i) adding an external shear at the liquid newlinesurface (either at the free or contaminated surface), (ii) applying an insoluble surfactant at the newlinefree surface, or liquid-liquid interface, (iii) contamination of the free surface by floating flexible newlineplate, (iv) bottom substrates are considered to be porous or slippery or wavy, by heating the newlinebottom wall uniformly, etc newline