A 2D vertical （2DV） numerical model, without o-coordinate transformation in the vertical direction, is developed for the simulation of flow and sediment transport in open channels. In the model, time-averaged Reynol...A 2D vertical （2DV） numerical model, without o-coordinate transformation in the vertical direction, is developed for the simulation of flow and sediment transport in open channels. In the model, time-averaged Reynolds equations are closed by the k-e nonlinear turbulence model. The modified Youngs- VOF method is introduced to capture free surface dynamics, and the free surface slope is simulated using the ELVIRA method. Based on the power-law scheme, the k-e model and the suspended-load transport model are solved numerically with an implicit scheme applied in the vertical plane and an explicit scheme applied in the horizontal plane. Bedload transport is modeled using the Euler-WENO scheme, and the grid-closing skill is adopted to deal with the moving channel bed boundary. Verification of the model using laboratory data shows that the model is able to adequately simulate flow and sediment transport in open channels, and is a good starting point for the study of sediment transport dynamics in strong nonlinear flow scenarios.展开更多
Understanding layer interplay is the key to utilizing layered heterostructures formed by the stacking of different two-dimensional materials for device applications. Boron nitride has been demonstrated to be an ideal ...Understanding layer interplay is the key to utilizing layered heterostructures formed by the stacking of different two-dimensional materials for device applications. Boron nitride has been demonstrated to be an ideal substrate on which to build graphene devices with improved mobilities. Here we present studies on the morphology and optical response of annealed few-layer hexagonal boron nitride flakes deposited on a silicon substrate that reveal the formation of linear wrinkles along well-defined crystallographic directions. The wrinkles formed a network of primarily threefold and occasionally fourfold origami-type junctions throughout the sample, and all threefold junctions and wrinkles formed along the armchair crystallographic direction. Furthermore, molecular dynamics simulations yielded, through spontaneous symmetry breaking, wrinkle junction morphologies that are consistent with both the experimental results and the proposed origami-folding model. Our findings indicate that this morphology may be a general feature of several two-dimensional materials under proper stress-strain conditions, resulting in direct consequences in device strain engineering.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.51579036,51579030)the Fundamental Research Funds for the Central Universities of China(No.DUT14YQ108)
文摘A 2D vertical （2DV） numerical model, without o-coordinate transformation in the vertical direction, is developed for the simulation of flow and sediment transport in open channels. In the model, time-averaged Reynolds equations are closed by the k-e nonlinear turbulence model. The modified Youngs- VOF method is introduced to capture free surface dynamics, and the free surface slope is simulated using the ELVIRA method. Based on the power-law scheme, the k-e model and the suspended-load transport model are solved numerically with an implicit scheme applied in the vertical plane and an explicit scheme applied in the horizontal plane. Bedload transport is modeled using the Euler-WENO scheme, and the grid-closing skill is adopted to deal with the moving channel bed boundary. Verification of the model using laboratory data shows that the model is able to adequately simulate flow and sediment transport in open channels, and is a good starting point for the study of sediment transport dynamics in strong nonlinear flow scenarios.
文摘Understanding layer interplay is the key to utilizing layered heterostructures formed by the stacking of different two-dimensional materials for device applications. Boron nitride has been demonstrated to be an ideal substrate on which to build graphene devices with improved mobilities. Here we present studies on the morphology and optical response of annealed few-layer hexagonal boron nitride flakes deposited on a silicon substrate that reveal the formation of linear wrinkles along well-defined crystallographic directions. The wrinkles formed a network of primarily threefold and occasionally fourfold origami-type junctions throughout the sample, and all threefold junctions and wrinkles formed along the armchair crystallographic direction. Furthermore, molecular dynamics simulations yielded, through spontaneous symmetry breaking, wrinkle junction morphologies that are consistent with both the experimental results and the proposed origami-folding model. Our findings indicate that this morphology may be a general feature of several two-dimensional materials under proper stress-strain conditions, resulting in direct consequences in device strain engineering.
