Electronic Thesis and Dissertation Repository


Master of Science


Mechanical and Materials Engineering


Roger E. Khayat


The natural convection of non-Fourier fluids of the dual-phase-lagging (DPL) type is examined. These fluids possess a relaxation time and a retardation time, reflecting the delay in the response of the heat flux and the temperature gradient with respect to one another. DPL fluids span a wide range of applications, including low-temperature liquids, fluids subjected to fast heat transfer processes, and nanofluids (NFs), for which both the relaxation and retardation times are expressed in terms of nanoparticle concentration and solution properties. Both stationary and oscillatory convection become equally probable as the relaxation time increases. A nonlinear spectral approach is also used to model the post-critical convective state for thermo-gravitational instability in a non-Fourier fluid of the single-phase-lagging (SPL) type heated from below. The Spectral approach reveals the number and type of required modes. It is found that the Cattaneo number increases the Nusselt number compared to a Fourier fluid.