Brown University School of Engineering

Fluids Seminar: Properties of Gold-Water Nanofluids Using Molecular Dynamics

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Tuesday, May 20, 2014 3:00pm - 4:00pm

Gianluca Puliti* University of Notre Dame Department of Aerospace and Mechanical Engineering Notre Dame, IN *Current affiliation: Piramal Critical Care, Inc. Properties of Gold-Water Nanofluids Using Molecular Dynamics Nanofluids belong to a new class of fluids with enhanced thermophysical properties and heat transfer performance. A broad spectrum of applications in science and engineering can potentially benefit from their use. However, the physical explanation for this enhancement is still lacking. The novelty of this work is in a fundamental, realistic, and comprehensive approach to the problem of understanding nanofluids through the use of molecular dynamics simulations with accurate potentials to effectively model realistic materials. Specifically, this study treats the case of a gold-water nanofluid at different particle volume fractions between 1%-vol and 15%-vol. In order to understand more fundamental physical phenomena at the gold-water interface, water confined between gold nanolayers will also be analyzed at different plate separations. Simulations make use of the Quantum Sutton-Chen (QSC) potential or Au-Au interactions, the Extended Simple Point-Charge (SPC/E) force field for water-water, and a modified Spohr potential for Au-water interactions. These potentials ensure that most of the physics is captured properly. Thermodynamics and transport properties will be discussed for all systems. It is interesting to note that while the thermodynamic properties of the mixture have been commonly predicted using ideal mixture theory, such predictions are found to be generally poor for nanofluids. Our results of computed properties indicate that values are between 10% and 400% off from ideal mixture predictions. The anisotropy induced by the gold-water interface, and its effects appear to be responsible for the disagreement. Transport properties, in particular shear viscosity, and thermal conductivity, are computed using novel equilibrium methods. Specifically, the present work adopts hybrid formulations that exploit the benefits of both Einstein and Green-Kubo classic relations, while avoiding the limitations of each. Transport properties are generally enhanced, and appear not to follow the predictions of classic theories.