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This paper describes the development and application of a 3-dimensional model of the barotropic and baroclinic circulation on the continental shelf west of Vancouver Island, Canada. A previous study with a 2D barotropic model and field data revealed that several tidal constituents have a significant baroclinic component (the K1 in particular). Thus we embarked on another study with a 3D model to study the baroclinic effects on the residual and several selected tidal constituents.The 3D model uses a harmonic expansion in time and a finite element discretization in space. All nonlinear terms are retained, including quadratic bottom stress, advection and wave transport (continuity nonlinearity). The equations are solved as a global and a local problem, where the global problem is the solution of the wave equation formulation of the shallow water equations, and the local problem is the solution of the momentum equation for the vertical velocity profile. These equations are coupled to the advection-diffusion equation for density so that density gradient forcing is included in the momentum equations. However, the study presented here describes diagnostic calculations for the baroclinic residual circulation only.The model is sufficiently efficient that it encourages sensitivity testing with a large number of model runs. In this sense, the model is akin to an extension of analytical solutions to the domain of irregular geometry and bottom topography where this parameter space can be explored in some detail.In particular, the consequences of the sigma coordinate system used by the model are explored. Test cases using an idealized representation of the continental shelf, shelf break and shelf slope, lead to an estimation of the velocity errors caused by interpolation errors inherent in the sigma coordinate system. On the basis of these estimates, the computational grid used in the 2D model is found to have inadequate resolution. Thus a new grid is generated with increased accuracy in the region of the shelf break. However, even with increased resolution, spurious baroclinic circulation seaward of the shelf break and in the vicinity of Juan de Fuca canyon remained a significant problem when the pressure gradient terms were evaluated using the σ coordinate system and using a realistic density profile.With the new grid, diagnostic calculations of the barotropic and baroclinic residual circulation are performed using forcing from the observed σt (density) field and from the gradient of this field. 相似文献
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A 3D finite-element model of the Adriatic tides 总被引:1,自引:0,他引:1
A 3D finite-element numerical model is applied to the Adriatic Sea to simulate its tidal motions. This fully nonlinear model includes a free surface, very realistic topography, and an advanced turbulence closure. Comparison with available tidal elevations at coastal stations and with tidal ellipses at a few locations in the open sea demonstrates that the model simulations are highly accurate. The results are then used to determine the 3D distribution of the tidal residual currents. 相似文献
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文章研究了乳山港区规划方案有关的潮流泥沙问题。首先分析了工程海域的自然条件,然后采用波浪潮流泥沙数学模型对乳山港区规划方案实施后的流场、航道淤积进行了模拟研究。研究结果表明,从周围水动力及泥沙环境考虑,该港区规划方案总体是可行的,但需注意拦门沙段航道淤积问题。 相似文献
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It is often advantageous to model a semi-enclosed estuarine or coastal embayment (e.g. fish farms or tidal inlets, or typhoon shelters) as a separate system within a larger water body connected to the outer sea. The water quality of the system depends crucially on its flushing time—the average time of a particle in the system. The flushing time is governed by the barotropic and baroclinic tidal exchanges between the system and the outer sea. We describe herein a general method to determine systematically the flushing time of a stratified water body via a numerical tracer experiment. Numerical solution of the 3D flow and mass transport equations for many practical problems show that the tracer mass removal process depends on the physical topography and bathymetry, tidal range and the degree of stratification in the outer sea. Field application suggests that the tracer mass variation can be well approximated by a double-exponential decay curve that can be described by three flushing coefficients. Using a simple analytical two-segment model, the flushing coefficients can be given a clear physical interpretation, and the flushing time can be easily determined in terms of the coefficients. The method is illustrated by application to a number of tidal inlets in Hong Kong, in both the dry and wet season. The connection between the numerically determined flushing time and the traditional bulk flushing time obtained from salt-balance methods is established. 相似文献
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The work presented in this paper is focused on the development of a simplified method to study the structural response of a deeply immersed cylinder subjected to the primary shock wave generated by an underwater explosion. The proposed analytical model is based on the string-on-foundation method initially developed by Hoo Fatt and Wierzbicki, who converted the two dimensional boundary value problem of a cylindrical shell to an equivalent one-dimensional problem of a plastic string on a plastic foundation. This method has already been extended by the authors to study the shock wave response of an unstiffened cylinder immersed in shallow water. The present work focuses on deep-immersed cylinders subjected to both high hydrostatic pressure and explosion shock wave. The elastic deformation energy of the cylinder under hydrostatic pressure is first calculated and used to determine the initial conditions of the dynamic problem. Cylinder deflection and plastic deformation energy are then calculated for various immersion depths. When confronted to numerical results, the proposed model appears to underestimate the increase of deflection and absorbed energy with the immersion depth. A thorough analysis of the results post-processed from Ls-Dyna/USA finite element simulations highlights a new mechanism which is due to the action of hydrostatic pressure that continues to push inward the immersed cylinder. In order to improve the analytical model, a correction factor on the hydrostatic pressure is introduced but it is finally concluded that a new mechanism dedicated to the late action of the hydrostatic pressure still needs to be developed. 相似文献
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防城港码头工程前后潮流场的数值模拟 总被引:1,自引:0,他引:1
基于双时间层的有限差分方法(ADI),建立了水深平均二维浅水潮流数学模型,采用逆风格式和追赶法求解二维浅水方程,在对模型进行潮位验证和潮流验证的基础上,对防城港码头工程实施前后的潮流场进行了数值模拟研究。研究表明:该工程建设不会减少湾内纳潮量,不会对海域水动力学条件产生较大影响,只会对码头附近产生较小影响。 相似文献
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港口建港条件评价是一项系统工程,从自然条件、技术条件、经济条件、城市港口及区域条件、社会及环境条件等5个方面进行评价。河口港建港条件的评价,既要符合一般港口的规律,也要考虑河口港的具体特点,取舍或重点突出某些对建港条件影响大的因素,形成合理的评价指标体系和评判标准。由于港口评价需要决策的目标多,模糊性强,对拟建港址建港条件的优劣做出准确的评判十分困难。文中采用系统工程的方法,把多目标决策技术中的模糊数学理论与层次分析方法结合起来,提出了河口港建港条件的多层次模糊综合评判模型。并以广州南沙港为例进行实证分析,研究情况与工程实际吻合较好,该项分析方法对今后类似工程评价具有良好的适应性。 相似文献
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针对船舶操纵模拟中的三维视景仿真的特点,开展船舶操纵模拟器中关于上海洋山港港区三维视景仿真的研究。以Google Earth提供的电子地形图像为基础,经过等高线和矢量化方法的处理,生成数字高程模型(Digital Elevation Model,DEM),并利用Multigen Creator建立直观的上海洋山港港区三维地形模型,再利用Vega的三维视景渲染功能对其进行渲染和驱动。根据该方法建立的上海洋山港港区三维视景模型库在模型精细度、逼真度和实时运算等方面,都能满足船员实操练习所需的条件。 相似文献
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为进一步完善洋山深水港的各项配套功能,港区北侧将通过围垦工程建设具有综合服务功能的物流园区。围垦工程将引起小洋山岛周围海域潮流及泥沙运动发生变化。为解决开发建设的一系列潮流泥沙技术难题,在充分掌握海域潮流泥沙运动特性的基础上,采用Mike21中的FM三角形网格和动边界技术建立平面二维潮流数学模型,模拟研究规划方案建设引起的潮流场变化,计算分析各围垦规划方案引起的潮流变化及泥沙冲淤幅度,论证规划方案的可行性。 相似文献