Browsing by Author "Tullius, Toni Kathleen"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Accelerated Discontinuous Galerkin Solvers with the Chebyshev Iterative Method on the Graphics Processing Unit
    (2011) Tullius, Toni Kathleen; Riviere, Beatrice M.; Warburton, Tim
    This work demonstrates implementations of the discontinuous Galerkin (DG) method on graphics processing units (GPU), which deliver improved computational time compared to the conventional central processing unit (CPU). The linear system developed when applying the DG method to an elliptic problem is solved using the GPU. The conjugate gradient (CG) method and the Chebyshev iterative method are the linear system solvers that are compared, to see which is more efficient when computing with the CPU's parallel architecture. When applying both methods, computational times decreased for large problems executed on the GPU compared to CPU; however, CG is the more efficient method compared to the Chebyshev iterative method. In addition, a constant-free upper bound for the DC spectrum applied to the elliptic problem is developed. Few previous works combine the DG method and the GPU. This thesis will provide useful guidelines for the numerical solution of elliptic problems using DG on the GPU.
  • Thumbnail Image
    Item
    Plasmonic Nanoparticle Laden Medium for Solar/Thermal Energy Storage
    (2015-08-13) Tullius, Toni Kathleen; Bayazitoglu, Yildiz; Dick, Andrew; Vajtai, Robert
    Nanofluids have become a popular way of increasing the efficiency in solar energy applications and enhancing the thermophysical properties of the fluid. This thesis contributes to the field of solar energy utilization by two distinct projects. The first part is a thermal analysis involving a single plasmonic nanoparticle, exposed to radiation, in a solid medium that undergoes phase change creating a liquid film around the particle. The temperature profiles for the particle, film, and solid medium are analyzed. It is shown that the larger particle heats faster, developing a smaller surrounding film; however, the integrity of the smaller particle will stay intact for longer. Compromise between the thermal resistance at the interface of the particle and film as well as the absorption from radiation in order to determine the proper particle type, size, and medium is studied. The effect of the inclusion of the particle/film interface resistance is clarified. In the second part of the thesis, a nanofluid mixture containing two or more different types of plasmonic nanoparticles, based on the absorption of the particles when exposed to radiation, is optimized. Because of the tunable plasmonic properties of metallic nanoparticles and the many possible variables to consider, two different optimization techniques were used in order to determining the correct recipe of nanoparticles submerged in water for a given temperature in order to get the maximum absorption. This contribution will help to determine which particle mixture would be required when exposed to radiation depending on the particular set of particles, size of particles, height of the container, concentration, and incident temperature.