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This paper addresses the experimental and numerical investigations of the dynamic parameters, natural frequencies and mode shapes, of fixed roof, ground supported, steel storage tanks. Three tall liquid storage tanks with aspect ratios greater than unity are considered. The considered tanks have similar height of 12.190 m and different radius of 6.095, 8.00, and 9.144 m. The effect of the aspect ratio, along with the liquid level on dynamic parameters is discussed. Finite element models of tanks are constructed using the finite element package ANSYS. The fluid-structure interaction is governed in the models. Yet, before using numerical techniques for analyzing the tank-liquid systems, they should be validated by experimental results. For this purpose, a series of ambient vibration tests are carried out to determine the natural frequencies and, if possible, the modes of the vibration. Comparison between numerical and experimental values shows good agreement. The new feature considered in the paper is the influence of roof on the natural frequencies and the modes of vibration. It is found that the influence of roof on the natural frequency of vibration of the considered tanks is negligible, while it does restrain the tank top against radial deformations and has significant effect on the mode shapes of tank.  相似文献   
2.
The main interest of the present study is the simulation of wind-induced currents in closed water bodies with shallow and deep regions. This paper describes a low time consumption numerical modelling technique for the simulation of free-surface flow over a geometrically complex bed. To achieve this, a technique employing coupled two- and three-dimensional flow solvers is developed for simulation of the flow. The conjunctive model consists of an upper part 2D Shallow Water Flow Solver (2D-SWFS) coupled with a 3D pseudo-compressible flow solver (3D-PCFS) for the deep regions with a proper interface boundary condition. The 2D-SWFS and 3D-PCFS solvers are coupled via an interfacial shear stress gradient and pressure effects. Time stepping is performed for the 2D solver, and an iterative procedure is employed by the 3D solver to satisfy the equilibrium constraints for the interfacial boundary. The model is able to consider 2D wetting and drying shallow regions without any underlying deep water. Both the 2D and 3D models use nodal based Galerkin finite volume method (GFVM) for solving the governing equations on the unstructured meshes. The accuracy of both models in solving the effective phenomena is examined by comparing the results of simulated test cases with readily available analytical solutions and experimental measurements. Finally, the accuracy of the conjunctive model is assessed by comparing its results for test cases with analytical solutions and experimental measurements from the literature. The new simulation method is then used to solve a wind-induced flow problem in a basin with deep water surrounded by shallow water parts.  相似文献   
3.
In the present paper the Galerkin finite volume method (FVM) is developed for solution of unsteady; two dimensional shallow water flow equations on unstructured triangular meshes. The numerical model considered two types of wetting and drying process which is an essential technique for modelling the tidal flow in the coastal zones with arbitrary topography. The use of triangular cells facilitates local refinement in the areas with considerable bed elevation variations. Hydrostatic pressure distribution was assumed and the effects of bed slope and friction are considered in two equations of motion. In order to damp out the unwanted numerical oscillations and reduction of instability of the numerical model and its stability during model running, the artificial viscosity was added to the formulation.The quality of the solution result and the accuracy of the applied model is assessed by comparison between numerical results and reported data in the literature for flow in a channel with spur dike which showed an average error of 6% with the experiment data. In addition to assure model accuracy and capability in wetting and drying situations, the current model was examined on an inclined bed with flooding and dewatering process. Numerical Result analysis showed that the second applied wet/dry technique enhanced outcomes from 5% average error to 3%. As a real world case study, Qeshm canal is considered in this study. In the Qeshm canal (located in the east part of the Persian Gulf) the flow pattern is formed by tidal currents via two open boundaries in the west and east ends. Besides, the computed water elevation and velocity at Kaveh port are compared with the available measurements for a period of time, in which the computed water elevation is much closer to the observed data rather than the computed velocity.  相似文献   
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A two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular mesh is developed for modeling density-dependent flow and transport through saturated-unsaturated porous media. The combined flow and transport model can handle a wide range of real-word problems, including the simulation of flow alone, contaminant transport alone, and combined flow and transport. Saltwater intrusion problems and instability caused by denser water on the top were investigated in this paper. Because the fundamental mechanism causing saltwater intrusion most likely is caused by density-induced convection and dispersion, the developed model is used to assess the interplay between density-driven flow and subsurface media through which the saltwater intrusion occurs.The mathematical formulation of the model is comprised of fluid flow and solute transport equations, coupled by fluid density. In the specific case of saltwater intrusion and unstable brine transport problems, this set of governing equation is non-linear and requires iterative methods to solve them simultaneously. Three case studies, which include a wide range of physical conditions, are used for verification of presented model and comparison with previously published solutions from other researchers presents encouraging agreements.  相似文献   
5.
A new approach for modeling discrete cracks in two-dimensional orthotropic media by the element free Galerkin method is described. For increasing the solution accuracy, recently developed orthotropic enrichment functions used in the extended finite element method are adopted along with a sub-triangle technique for enhancing the Gauss quadrature accuracy near the crack. An appropriate scheme for selecting the support domains near a crack is employed to reduce the computational cost. In this study, mixed-mode stress intensity factors are obtained by means of the interaction integral to determine the fracture properties. Several problems are solved to illustrate the effectiveness of the proposed method and the results are compared with available results of other numerical or (semi-) analytical methods.  相似文献   
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The process of local scour around bridge piers is fundamentally complex due to the three-dimensional flow patterns interacting with bed materials. For geotechnical and economical reasons, multiple pile bridge piers have become more and more popular in bridge design. Although many studies have been carried out to develop relationships for the maximum scour depth at pile groups under clear-water scour condition, existing methods do not always produce reasonable results for scour predictions. It is partly due to the complexity of the phenomenon involved and partly because of limitations of the traditional analytical tool of statistical regression. This paper addresses the latter part and presents an alternative to the regression in the form of artificial neural networks, ANNs, and adaptive neuro-fuzzy inference system, ANFIS. Two ANNs model, feed forward back propagation, FFBP, and radial basis function, RBF, were utilized to predict the depth of the scour hole. Two combinations of input data were used for network training; the first input combination contains six-dimensional variables, which are flow depth, mean velocity, critical flow velocity, grain mean diameter, pile diameter, distance between the piles (gap), besides the number of piles normal to the flow and the number of piles in-line with flow, while the second combination contains seven non-dimensional parameters which is a composition of dimensional parameters. The training and testing experimental data on local scour at pile groups are selected from several precious references. Networks’ results have been compared with the results of empirical methods that are already considered in this study. Numerical tests indicate that FFBP-NN model provides a better prediction than the other models. Also a sensitivity analysis showed that the pile diameter in dimensional variables and ratio of pile spacing to pile diameter in non-dimensional parameters are the most significant parameters on scour depth.  相似文献   
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