Zhang C.,Shanghai Rules and Research Institute |
Zhang C.,South China University of Technology |
Lin N.,South China University of Technology |
Tang Y.,Center for Maritime Engineering |
Zhao C.,South China University of Technology
Computers and Fluids | Year: 2014
In this study, a finite difference model for the viscous incompressible Navier-Stokes (N-S) equations is developed to investigate problems with respect to wave-structure interaction. A two-step projection algorithm is employed to discretize the N-S equations on a fixed Cartesian grid. Coupled with wave generating and absorbing options, the model captures free surfaces using a volume-of-fluid method with a second-order piecewise linear interface construction (PLIC-VOF). In addition, a second-order sharp interface immersed boundary (SI-IB) method is utilized to account for the no-slip boundary condition on structure surfaces. The new model is capable of simulating free surface flows and their interaction with a stationary or moving structure, and wave generating and absorbing options are available in the model for some specific cases. To validate the model from different aspects, a series of numerical experiments are conducted. These tests include an oscillating cylinder in fluid without a free surface, liquid sloshing in a tank, water exit and entry of a horizontal cylinder, some wave generation and absorption tests, and a solitary wave over a submerged rectangular obstacle. Excellent agreement is obtained when the results are compared to analytical, experimental and other numerical results. Furthermore, two cases of a submerged and a semi-submerged ellipse rotating in a tank are investigated, and some significant phenomena are observed. © 2013 Elsevier Ltd.
Han W.,Center for Nanoscale Science and Technology |
Han W.,Center for Maritime Engineering |
Yu Y.,Center for Nanoscale Science and Technology |
Tang Y.,Center for Nanoscale Science and Technology |
And 2 more authors.
Materials Performance and Characterization | Year: 2014
We experimentally report material design of halloysite nanotube (HNT)/epoxy composites, focusing on the effects of HNT concentration on thermal and mechanical properties, especially fracture toughness, of diverse epoxy composites with as-received and phenylphosphonic-acid (PPA)-treated HNTs prepared by mechanical mixing or ball-milling homogenization. It is demonstrated that, with HNT added in the region of 0.0-10.0 wt. %, significantly reinforced fracture toughness of the epoxy composites can be achieved. The epoxy composites prepared by ball-milling homogenization have much more uniform HNT size and dispersion than those prepared by simple mechanical mixing, enhancing their fracture toughness. The morphology of treated HNTs changes from nanotubes to nanoplatelets; as a result, with a substantial increase in the total contact area between HNT and epoxy and enhancing the fracture toughness of epoxy composites. This higher HNT concentration and the higher fracture toughness are achieved for various epoxy composites. However, the optimal concentration of HNT is 5.0 wt. % in this study. The addition of further HNT achieves only marginal fracture toughness enhancement and more negative effects appear, such as HNT concentration gradient in cured epoxy composites, high potential decrease in glass transition temperature (Tg), and potential immature tensile failure. Copyright © 2014 by ASTM International.