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Abstract:
This study examines mixing characteristics of double-diffusive convection for a wide range of fluids. Our approach involves Direct Numerical Simulation (DNS) utilizing de-aliased pseudo-spectral method. To expedite these simulations the numerical algorithm was parallelized using Message Passing Interface (MPI) calculations in both two and three dimensions. A theoretical model of equilibrium double-diffusive transport is presented, which emphasizes the role of secondary instabilities of salt fingers in saturation of their linear growth. Theory assumes that the fully developed equilibrium state is characterized by the comparable growth rates of primary and secondary instabilities. This assumption makes it possible to formulate a simple and efficient algorithm for computing diffusivities of heat and salt as a function of the background property gradients and molecular parameters. The model predicts that the double-diffusive transport of heat and salt rapidly intensifies with decreasing density ratio. Fluxes are less sensitive to molecular characteristics, mildly increasing with Prandtl number (Pr) and decreasing with diffusivity ratio ( ). Theory is successfully tested by a series of direct numerical simulations which span a wide range of Pr and . Double diffusion occurs on the micro-scale and computer technology is just now reaching the processing speeds needed to fully resolve this complex phenomenon in three dimensions. In addition to the well-known salt fingering within the oceans, double diffusion occurs in many other statically stable regions, both terrestrially and beyond our atmosphere. Understanding this phenomenon could prove essential as we continue to discover new worlds and new areas within our galaxy, including here on terra firma.
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Master's thesis |
| Pages: |
81 |
| Report Date: |
JUN 2011 |
| Report Number: |
A299745 |
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