Abstract:
The main focus of this thesis has been to understand the dynamics of salt-diapiric
structures and the role of various parameters that govern the diapir structures with the help of
Rayleigh-Taylor fluid instability. Rayleigh-Taylor instability occurs in the presence of two fluid
layers with different viscosity and density.
In this work, we present results from 2-D numerical simulations and laboratory model
experiments to explain characteristics of salt-diapirs and its dependence on governing
parameters. We in this study considered a two-layer system that contains heavier layer fluid
lying over lighter fluid layer and these layers are of different thickness. For simulating this
system, a code based on finite volume discretization and semi implicit method for pressure
linked equations revised (SIMPLER) algorithm is used. Initial condition is a step-profile for
concentration (density) with heavier fluid (representing sedimentary soil layer) laying-over
lighter fluid layer (representing evaporative mineral layer) and is allowed to evolve in time due
to diffusion and convection. Resulting Rayleigh-Taylor fluid instability helps in understanding
characteristics of salt-diapirs on various governing parameters.
We have also done experiments with similar configuration in a tank in which an initial
step change in density across an interface (stable) is established using two layers of fluids with
different densities and high viscosities. We used CMC (Carboxy Methyl Cellulose) to vary the
viscosity of the water and sugar to increase the density. The unstable density stratification was
obtained by inverting the tank. Experiments are done with different density difference and layer
thickness ratios. Experimental results provide quantitative verification of the simulations.
