共查询到20条相似文献，搜索用时 609 毫秒
1.
P.M. CiancioJ.A. Reyes 《Ocean Engineering》2003,30(11):1323-1333
This paper deals with the determination of the critical load in the buckling of isotropic, circular annular thin plates whose thickness varies slightly according to an exponential law.The outer edge of the plate is elastically restrained against rotation while the inner boundary is free. Classical small-deflection theory is used. An hidrostatic pressure acting in the middle plane is considered.The eigenvalues of the problem are obtained by means of an analytical approach based on the optimized Rayleigh-Ritz method. It is shοwnι that the results are in good agreement from an engineering viewpoint, with those available in the literature. 相似文献
2.
In this study, we derive an analytical solution for long waves over a circular island which is mounted on a flat bottom. The water depth on the island varies in proportion to an arbitrary power, γ, of the radial distance. Separation of variables, Taylor series expansion, and Frobenius series are used to find the solutions, which are then validated by comparing them with previously developed analytical solutions. We also investigate how different wave periods, radii of the island toe, and γ values affect the solutions. For a circular island with a small value of γ (e.g. γ = 2/3, as in the equilibrium beach (Bruun, 1954)), the wave rays approaching near the island center reach the coastline, whereas the rays approaching away from the center bend away from the coastline, leading to smaller wave amplitudes along the coast. However, for a circular island with a large value of γ, e.g. γ = 2, all the rays on the island reach the coast, giving large coastline wave amplitudes. If the island domain is small compared to the wavelength, the wave amplitudes on the coastline do not increase significantly; however, when the island domain is not small, the wave amplitudes increase significantly. If γ is also large, the amplitudes can be so large as to cause a disaster on the island. 相似文献
3.
波浪在传播过程中遇到岛屿就会发生绕射。本文使用混合元方法对修正型缓坡方程进行了数值求解,并与KUO et al的解析解进行了比较验证。在此基础上研究了工程尺度背景下,波浪在三维圆形岛地形上的绕射,计算了不同入射波浪周期、浅滩形状参数和岛屿尺寸情况下,沿波浪传播方向断面上和岛屿岸线上的相对波高大小。计算结果表明：随着入射波周期的减小、浅滩形状参数的增大和岛屿尺寸的减小,圆形岛迎浪侧的相对波高振荡幅度、圆形岛背浪侧的相对波高大小以及岛屿岸线上的相对波高振幅和大小均随之增大。不同情况下,岛屿岸线上的相对波高最大值大多数发生在迎浪点,个别发生在迎浪点两侧20°~25°处;最小值发生在背浪点两侧30°附近。 相似文献
4.
Simply supported or clamped boundary conditions are rather ideal situations difficult to satisfy from a physical viewpoint. This paper considers a more “moderate” restriction: the case of edges elastically restrained against rotation for which no exact solution appears in the open literature. Eigenvalues corresponding to a wide range of the intervening geometric and mechanical parameters are determined. Good agreement is obtained with frequency coefficients determined two decades ago by means of a variational method. Obviously the problem is of basic interest in many ocean engineering applications: from the design of certain underwater acoustic transducers to pump and compressor elements passing through the design of naval vehicles and ocean structures. 相似文献
5.
The paper analyzes the elastic deflection of submerged pipelines laid with a stinger by taking into account the overall effects of the ovalization of the cross section. The analysis is performed by means of a singular perturbation technique and the analytical solution obtained is shown to offer different advantages over the finite element method. Two examples demonstrate the effectiveness of the procedure by means of a comparison with results from other less refined analytical solutions and from the commercial finite element code
. 相似文献
6.
One-dimensional stock cutting problems can be encountered at the production stage of many areas of engineering as well as in shipbuilding and coastal structures. In this paper, a novel approach is proposed to solve the problem directly by using the cutting patterns obtained by the analytical methods at the mathematical modeling stage. By minimizing both the number of different cutting patterns and material waste, the proposed method is able to capture the ideal solution of the analytical methods. The main advantage of the method comes from the fact that an integer solution is guaranteed. However, in analytical methods it is not always possible to produce integer solutions and the linear programming algorithm must be run repeatedly to select integer solutions from the alternatives to get practical results. The proposed nesting algorithm is a low-cost and efficient tool. Minimizing the number of cutting patterns contributes to time and material savings. Also, by using this method trim loss is minimized and stock usage is maximized. The efficiency of the proposed method is demonstrated by extensive numerical results. 相似文献
7.
This paper considers the numerical simulation of nonlinear wave run-up within a highly accurate Boussinesq-type model. Moving wet–dry boundary algorithms based on so-called extrapolating boundary techniques are utilized, and a new variant of this approach is proposed in two horizontal dimensions. As validation, computed results involving the nonlinear run-up of periodic as well as transient waves on a sloping beach are considered in a single horizontal dimension, demonstrating excellent agreement with analytical solutions for both the free surface and horizontal velocity. In two horizontal dimensions cases involving long wave resonance in a parabolic basin, solitary wave evolution in a triangular channel, and solitary wave run-up on a circular conical island are considered. In each case the computed results compare well against available analytical solutions or experimental measurements. The ability to accurately simulate a moving wet–dry boundary is of considerable practical importance within coastal engineering, and the extension described in this work significantly improves the nearshore versatility of the present high-order Boussinesq approach. 相似文献
8.
In this study, the Navier-Stokes equations and the pressure Poisson equation for two-dimensional time-dependent viscous flows are solved with a finite difference method in a curvilinear coordinate system. With this numerical procedure, the vortex shedding flow past a circular cylinder near a wall is investigated. The flow is calculated for a broad range of gap ratios for different Reynolds numbers ranging from 80 to 1000. Based on the numerical solutions, the vortex shedding is observed using various methods, and the mechanism for the vortex shedding suppression at small gap ratios is analyzed. The critical gap ratio at which the vortex shedding is suppressed is identified at different Reynolds numbers. 相似文献
9.
Numerical study of combined overflow and wave overtopping over a smooth impermeable seawall 总被引：1，自引：0，他引：1
A numerical wave flume is used to investigate the discharge characteristics of combined overflow and wave overtopping of impermeable seawalls. The numerical procedure computes solutions to the Reynolds-averaged Navier–Stokes equations and includes the generation of an irregular train of waves, the simulation of wave breaking and interaction with a sloping, impermeable wall. The numerical model is first tested against published experimental observations, approximate analytical solutions and empirical design formulae for the cases of pure overflow and pure overtopping. A sequence of numerical experiments simulating combined overflow and overtopping are described. The results are used to determine empirical discharge formulae of the form used in current practice. 相似文献
10.
Two types of analytical solutions for waves propagating over an asymmetric trench are derived. One is a long-wave solution and the other is a mild-slope solution, which is applicable to deeper water. The water depth inside the trench varies in proportion to a power of the distance from the center of the trench (which is the deepest water depth point and the origin of x-coordinate in this study). The mild-slope equation is transformed into a second-order ordinary differential equation with variable coefficients based on the longwave assumption [Hunt's, 1979. Direct solution of wave dispersion equation. Journal of Waterway, Port, Coast. and Ocean Engineering 105, 457–459] as approximate solution for wave dispersion. The analytical solutions are then obtained by using the power series technique. The analytical solutions are compared with the numerical solution of the hyperbolic mild-slope equations. After obtaining the analytical solutions under various conditions, the results are analyzed. 相似文献
11.
One-dimensional stock-cutting problem is a commonly encountered problem not only in shipbuilding and construction of coastal structures, but also in other engineering applications related to production and construction. The proposed approach achieves results using cutting patterns directly whereas analytical methods first need to establish a mathematical model. While obtaining ideal solutions of the analytical methods, the new approach limits the wastage to a minimum number of stock materials. In addition, the new approach allows the use of different sized stock materials while it creates various options for the use of single sized stock materials. Use of different sized stock materials broadens the point of view for the solution compared to the use of single sized stock material. Moreover, the new method yields integer results whereas the analytical methods using linear programming usually produce impractical non-integer results. To obtain integer results, the analytical methods need to solve the problem multiple times and screen the alternative solutions. 相似文献
12.
The free vibration analysis of submerged cantilever plates 总被引：3，自引：0，他引：3
Based on empirical added mass formulation, this work presents a simple procedure to determine the vibration frequencies and mode shapes of submerged cantilever plates. Once the added mass formulation is derived, the procedure can be used to analyze free vibration response easily. An analytical and numerical study is also performed for the vibrations of cantilever plates in air and in water, with these results compared with experimental and numerical data from pertinent literature. Besides, the frequency parameters of the submerged plate for various aspect ratios and thickness ratios are given in design data sheet form and are appropriate for engineering design applications. 相似文献
13.
In this paper, we present a numerical procedure for solving a 2‐dimensional, compressible, and nonhydrostatic system of equations. A forward‐backward integration scheme is applied to treat high‐frequency and internal gravity waves explicitly. The numerical procedure is shown to be neutral in time as long as a Courant–Friedrichs–Lewy criterion is met. Compared to the leap‐frog‐scheme most models use, this method involves only two time steps, which requires less memory and is also free from unstable computational modes. Hence, a time‐filter is not needed. Advection and diffusion terms are calculated with a time step longer than sound‐wave related terms, so that extensive computer time can be saved. In addition, a new numerical procedure for the free‐slip bottom boundary condition is developed to avoid using inaccurate one‐sided finite difference of pressure in the surface horizontal momentum equation when the terrain effect is considered. We have demonstrated the accuracy and stability of this new model in both linear and nonlinear situations. In linear mountain wave simulations, the model results match the corresponding analytical solution very closely for all three cases presented in this paper. The analytical streamlines for uniform flow over a narrow mountain range were obtained through numerical integration of Queney's mathematical solution. It was found Queney's original diagram is not very accurate. The diagram had to be redrawn before it was used to verify our model results. For nonlinear tests, we simulated the famous 1972 Boulder windstorm and a bubble convection in an isentropic enviroment. Although there are no analytical solutions for the two nonlinear tests, the model results are shown to be very robust in terms of spatial resolution, lateral boundary conditions, and the use of the time-split scheme. 相似文献
14.
Feng Weibing Hong Guangwen
Ph. D Student Hohai University Nanjing .
Professor Hohai University Nanjing 《中国海洋工程》1995,(1)
An analytic-numerical solution of wave transformation in shoaling water is presented in this paper. The analytical expression for wave heights along the wave rays is derived in consideration of the combined effect of water depth shoaling, the wave refraction and the sea bottom friction. The wave rays (orthogonals) are calculated by a fourth order Runge-Kutta algorithm and the wave crest lines are computed by an iteration procedure. The numerical results are compared with analytical solution for a special case of parallel- straight contour shore and field data, and comparisons show that the proposed mathematical model and computation method are very useful and convenient for engineering application. 相似文献
15.
Stability design of submarine pipelines is a very important procedure in submarine pipeline engineering design. The calculation of hydrodynamic forces caused by waves and currents acting on marine pipelines is an essential step in pipeline design for stability. The hydrodynamic forces-induced instabilities of submarine pipelines should be regarded as a wave/ current-pipeline-seabed interaction problem. This paper presents a review on hydrodynamic forces and stability research of submarine pipelines under waves and currents. The representative progress including the improved design method and guideline has been made for the marine pipelines engineering design through experimental investigations, numerical simulations and analytical models. Finally, further studies on this issue are suggested. 相似文献
16.
ABSTRACTThe elastic mechanical response of porous materials under a heat source has many applications in civil engineering and has received considerable attention in the geotechnical literature. In this paper, a Kelvin viscoelastic model is combined with the thermohydromechanical governing equations for marine clay and solved using a numerical inversion of the inverse Laplace transform in the time domain. After validation against existing analytical solutions, numerical parametric studies are conducted to investigate the influence of viscosity on temperature, excess pore pressure, and displacement. It is shown that viscosity has little influence on temperature, a modest influence on displacements, and a quite significant influence on excess pore pressure. 相似文献
17.
海冰板的环形屈曲的压缩破坏 总被引：2，自引：0，他引：2
在轴对称条件下，给出海冰板的环向屈曲面临载荷，从细观力学的观点分析了微裂纹开裂的条件，扩展方向并给出绕海洋平台柱腿冰的损伤区的尺度。所给出的临界半径是一个与冰材料力学特征，冰的微结构参数一海洋平台柱腿半径相关的特征参数。对现场所观察和测量的结构给出了解释和定量分析。 相似文献
18.
考虑土骨架加速度效应的海床动力反应及其影响因素分析 总被引：2，自引：0，他引：2
由Biot二维广义动力固结理论的形式基本控制方程出发,忽略孔隙流体的加速度,提出了饱和海床动力反应的时域有限元数值解法.联立静力平衡条件和Biot固结方程的退化法所得到的数值解可视为其特例.在比较算例中,退化法得到的超静孔压和有效应力幅值沿海床深度的分布与解析解一致.一般情况下,土骨架的加速度对海床的有效应力和超静孔压影响很小,控制方程可以退化为Biot理论.成层海床上部的粗砂层不会使超静孔压幅值在海床表面下较浅的深度内迅速衰减,难以改变海床的瞬时循环液化深度. 相似文献
19.
P.D. Scarlatos 《Coastal Engineering》1982,6(1):27-45
The Saint-Venant system of partial differential equations is solved by a pure finite-element method, in which integrations in both space and time are performed by utilizing Galerkin's procedure. With a special treatment of the non-linear terms, the problem is finally reduced to a linear system of algebraic equations that is solved by the conjugate gradient algorithm. This implicit scheme is proved, by numerical experiments, to be unconditionally stable. The reliability of the method is investigated by comparison of the numerical results with experimental data. Also the accuracy of the model is tested against analytical solutions for simplified cases of the unsteady free surface flow equations. 相似文献
20.
The three-dimensional numerical model with σ-coordinate transformation in the vertical direction is applied to the simulation of surface water waves and wave-induced laminar boundary layers. Unlike most of the previous investigations that solved the simplified one-dimensional boundary layer equation of motion and neglected the interaction between boundary layer and outside flow, the present model solves the full Navier–Stokes equations (NSE) in the entire domain from bottom to free surface. A non-uniform mesh system is used in the vertical direction to resolve the thin boundary layer. Linear wave, Stokes wave, cnoidal wave and solitary wave are considered. The numerical results are compared to analytical solutions and available experimental data. The numerical results agree favorably to all of the experimental data. It is found that the analytical solutions are accurate for both linear wave and Stokes wave but inadequate for cnoidal wave or solitary wave. The possible reason is that the existing analytical solutions for cnoidal and solitary waves adopt the first-order approximation for free stream velocity and thus overestimate the near bottom velocity. Besides velocity, the present model also provides accurate results for wave-induced bed shear stress. 相似文献