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Piroz Zamankhan 《Communications in Nonlinear Science & Numerical Simulation》2012,17(12):5273-5285
Low-head dams exist in many rivers for the purposes of diverting water for open-channel irrigation and providing power plants with cooling water. Flow over low-head dams is quite complex and dangerous rollers often develop down-stream that tend to trap and submerge floating objects. This paper presents an analysis of the problem based on physical and computational fluid dynamics (CFD) modeling and the result of this analysis in the form of design suggestions intended to diminish the hazards associated with rollers. 相似文献
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In a series of experiments, a granular material in a rectangular container with two hollow cylinders was studied as it underwent horizontal vibrations. At the peak values of acceleration, novel swirling granular flows were observed in the cylinders while the grains cascaded down the outer surface of the piles that formed outside the cylinders. Computer simulations were performed that supported our interpretation of the behaviour observed in the experiments. 相似文献
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Piroz Zamankhan 《Applied Mathematical Modelling》2012,36(1):414-429
A series of experiments are described in which bubbles and solid structures are produced in a highly agitated bed of vertically shaken granular materials. To identify the physical mechanisms behind bubbling, three-dimensional simulations of the aforementioned systems are performed on a graphics processing unit (GPU). The gas dynamics above and within shaken granular materials is solved using large-eddy simulations (LES) while the dynamics of grains is described through molecular dynamics. Here, the interaction between the grain surfaces is modeled using the generalized form of contact theory developed by Hertz. In addition, the coefficient of kinetic friction is assumed to depend on the relative velocity of slipping. The results show both a qualitative and a quantitative agreement between simulations and experiments. They imply that the instantaneous formation and failure of granular aggregates could play an important role in the nucleation, growth, departure and collapse of bubbles in shaken granular materials. This promising effort in GPU computing may position the GPU as a compelling future alternative to traditional simulation techniques. 相似文献
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Douville NJ Zamankhan P Tung YC Li R Vaughan BL Tai CF White J Christensen PJ Grotberg JB Takayama S 《Lab on a chip》2011,11(4):609-619
Studies using this micro-system demonstrated significant morphological differences between alveolar epithelial cells (transformed human alveolar epithelial cell line, A549 and primary murine alveolar epithelial cells, AECs) exposed to combination of solid mechanical and surface-tension stresses (cyclic propagation of air-liquid interface and wall stretch) compared to cell populations exposed solely to cyclic stretch. We have also measured significant differences in both cell death and cell detachment rates in cell monolayers experiencing combination of stresses. This research describes new tools for studying the combined effects of fluid mechanical and solid mechanical stress on alveolar cells. It also highlights the role that surface tension forces may play in the development of clinical pathology, especially under conditions of surfactant dysfunction. The results support the need for further research and improved understanding on techniques to reduce and eliminate fluid stresses in clinical settings. 相似文献
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Piroz Zamankhan 《Shock Waves》2008,17(5):337-349
Large scale, three dimensional computer simulations of monosized, viscoelastic, spherical glass particles flowing in an inclined
duct were performed using a phenomenological model based on the modified Kelvin–Maxwell model. The particle flow rate in the
model duct was regulated using a stationary wedge located in the middle of the duct. At low flow rates of glass particles,
a continuous flow was observed similar to that excited by steadily and rapidly adding glass particles to the top of a heap.
However, at high flow rates, a totally different situation arises where a flow with a different nature was established in
the duct. The situation was found to be analogous to the case of a supersonic gas flow in a duct, where a curved-bow shock
was observed to have formed on the upper edges of the duct adjacent to the wedge. In addition, in supersonic granular flows
the viscous and conductance effects spread the shock changes over a finite shock layer. 相似文献
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Piroz Zamankhan 《Communications in Nonlinear Science & Numerical Simulation》2012,17(11):4224-4240
Experimental and numerical studies are described in which a thin film of air-immersed grains is spun in vertical and tilted containers about their axis. At high rotation rates a steep depression appears around the axis of rotation. Interesting fractal type patterns with dimension D = 1.7 ± 0.05 are observed at the air-grain interfaces in the depression. By utilizing computer simulations, it is shown that the fractal-like patterns may be associated with a sharp deformation of the volume occupied by the particles within the depression hole due to turbulent diffusion. 相似文献
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A. Jafari P. Zamankhan S.M. Mousavi P. Kolari 《Communications in Nonlinear Science & Numerical Simulation》2009,14(4):1396-1402
In order to understand the normal and pathologic behavior of the human vascular system, detailed knowledge of blood flow and the response of blood vessels is required. In fact the ability to predict the flow hydrodynamics at any site in the vessels can lead to a better understanding of the behavior of blood flow. Simulation can play an important role in understanding the hemodynamic forces. The objective of the present attempt was to simulate the behavior of blood flow in microvessels using computational fluid dynamics (CFD). Numerical analysis is performed using a commercially available CFD package Fluent 6.2 which is based on the finite volume method. A continuum approach is proposed in which fluid structure interaction has been taken into account. Based on limitations imposed by computational resources, a more simplified model based on volume of fluid (VOF) approach is suggested to simulate movements of RBCs in capillaries and also to predict RBCs’ deformation. Three-dimensional incompressible laminar flow fields are obtained by solving continuity and Navier–Stokes equations computationally. It was found that multiphase CFD simulations may give further insight into the dynamic characteristics of blood flow under complex flow conditions. 相似文献
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