COMPUTATIONAL FLUID DYNAMICS MODELING OF A SUBMERGED BODY IN A TOW TANK WITH WAVE GENERATION

A computational fluid dynamics (CFD) model of the NPS tow tank with wave generation and a submerged body was created to investigate different methods of solid body modeling using commercial CFD software ANSYS CFX. A comparison of the rigid body method and immersed solid method was performed modeling a submerged rectangular body at different depths and different orientations. The models produced similar results when the body was lower beneath the wave surface with limited fluid-body interaction. As the amount of fluid-body interaction increased, the rigid body method showed increased amounts of wave energy dissipation as compared to the immersed solid method. This disruption of the wave energy resulted in the rigid body method showing lower body forces and moments when compared to the immersed solid model. The increased wave energy dissipation in the rigid body model is likely caused by the different mechanism for modeling body-fluid interaction. Future studies should compare the immersed solid modeling method results to experimental data and develop a CFD model with body motion.Outstanding ThesisLieutenant Commander, United States NavyApproved for public release. distribution is unlimite

Cold sprayed Coatings with Dual Nanoparticle Reinforcements for Wear and Corrosion Protection

NPS-19-M26

Synthesis and corrosion behavior of cold sprayed dual nanoparticle T reinforced Al coatings

The article of record as published may be found at https://doi.org/10.1016/j.surfcoat.2020.126280This study investigates the synergistic and individual effects of nano boron carbide (nB4C) and boron nitride nanoplatelets (BNNP) on the corrosion behavior of cold spray aluminum matrix composite (MMC) coatings. Cryomilling and cold spraying were used to synthesize four novel Al MMC coatings with reinforcements consisting of either 2 vol.% nB4C, 2 vol.% BNNP, or dual nanoparticle reinforcement consisting of 1 vol.% nB4C plus 1 vol.% BNNP. Cold sprayed coatings were evaluated using microhardness testing which revealed an 11.7% increase in hardness in the dual nanoparticle reinforced composite coating. Coatings were subjected to 500 h and 2000 h corrosion tests in a salt fog chamber consisting of 3.5% NaCl to simulate an aggressive marine environment. Coatings were evaluated post-salt fog chamber by mass and thickness change measurements, optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. Following 500 h corrosion testing, each composite coating experienced mild to severe pitting throughout a significant portion of the coating. Following 2000 h exposure, in addition to severe pitting, all coatings experienced galvanic corrosion at the coating/substrate interface.AN acknowledges support from the Naval Postgraduate School thru the Research Initiation Program (RIP) and from the NPS Foundation thru a SEED Phase II grant.AN acknowledges support from the Naval Postgraduate School thru the Research Initiation Program (RIP) and from the NPS Foundation thru a SEED Phase II grant