共查询到10条相似文献，搜索用时 125 毫秒
1.
A temporally second-order accurate Godunov-type scheme for solving the extended Boussinesq equations
A numerical scheme for solving the class of extended Boussinesq equations is presented. Unlike previous schemes, where the governing equations are integrated through time using a fourth-order method, a second-order Godunov-type scheme is used thus saving storage and computational resources. The spatial derivatives are discretised using a combination of finite-volume and finite-difference methods. A fourth-order MUSCL reconstruction technique is used to compute the values at the cell interfaces for use in the local Riemann problems, whilst the bed source and dispersion terms are discretised using centred finite-differences of up to fourth-order accuracy. Numerical results show that the class of extended Boussinesq equations can be accurately solved without the need for a fourth-order time discretisation, thus improving the computational speed of Boussinesq-type numerical models. The numerical scheme has been applied to model a number of standard test cases for the extended Boussinesq equations and comparisons made to physical wave flume experiments. 相似文献
2.
The present study develops a numerical model of the two-dimensional fully nonlinear shallow water equations （NSWE） for the wave run-up on a beach. The finite volume method （FVM） is used to solve the equations, and a second-order explicit scheme is developed to improve the computation efficiency. The numerical fluxes are obtained by the two dimensional Roe＇ s flux function to overcome the errors caused by the use of one dimensional fluxes in dimension splitting methods. The high-resolution Godunov-type TVD upwind scheme is employed and a second-order accuracy is achieved based on monotonic upstream schemes for conservation laws （MUSCL） variable extrapolation; a nonlinear limiter is applied to prevent unwanted spurious oscillation. A simple but efficient technique is adopted to deal with the moving shoreline boundary. The verification of the solution technique is carried out by comparing the model output with documented results and it shows that the solution technique is robust. 相似文献
3.
Based on a wave bottom boundary layer model and a sediment advection-diffusion model, seven turbulence schemes are compared regarding their performances in prediction of near-bed sediment suspension beneath waves above a plane bed. These turbulence algorithms include six empirical eddy viscosity schemes and one standard two-equation k-ε model. In particular, different combinations of typical empirical formulas for the eddy viscosity profile and for the wave friction factor are examined. Numerical results are compared with four laboratory data sets, consisting of one wave boundary layer hydrodynamics experiment and three sediment suspension experiments under linear waves and the Stokes second-order waves. It is shown that predictions of near-bed sediment suspension are very sensitive to the choices of the empirical formulas in turbulence schemes. Simple empirical turbulence schemes are possible to perform equally well as the two-equation k-ε model. Among the empirical schemes, the turbulence scheme, combining the exponential formula for eddy viscosity and Swart formula for wave friction factor, is the most accurate. It maintains the simplicity and yields identically good predictions as the k-ε model does in terms of the wave-averaged sediment concentration. 相似文献
4.
不同TVD 格式对内孤立波数值模拟结果影响研究 总被引：1，自引：0，他引：1
为了研究不同TVD格式对内孤立波模拟结果的影响,利用改进后的SUNTANS三维非静压海洋模型,通过理想算例和南海东北部海域内孤立波的模拟,比较分析了求解温盐方程TVD格式的4种经典通量限制函数(superbee, minmod, van Leer和MUSCL)对计算结果的影响。综合理想算例和南海东北部海域模拟结果,在所讨论的4种通量限制函数中,利用MUSCL限制函数所得模拟结果最优,建议在南海东北部海域内孤立波模拟中采用MUSCL限制函数。 相似文献
5.
W. E. Rogers J. M. Kaihatu H. A. H. Petit N. Booij L. H. Holthuijsen 《Ocean Engineering》2002,29(11):1357-1390
The numerical schemes for the geographic propagation of random, short-crested, wind-generated waves in third-generation wave models are either unconditionally stable or only conditionally stable. Having an unconditionally stable scheme gives greater freedom in choosing the time step (for given space steps). The third-generation wave model SWAN (“Simulated WAves Nearshore”, Booij et al., 1999) has been implemented with this type of scheme. This model uses a first order, upwind, implicit numerical scheme for geographic propagation. The scheme can be employed for both stationary (typically small scale) and nonstationary (i.e. time-stepping) computations. Though robust, this first order scheme is very diffusive. This degrades the accuracy of the model in a number of situations, including most model applications at larger scales. The authors reduce the diffusiveness of the model by replacing the existing numerical scheme with two alternative higher order schemes, a scheme that is intended for stationary, small-scale computations, and a scheme that is most appropriate for nonstationary computations. Examples representative of both large-scale and small-scale applications are presented. The alternative schemes are shown to be much less diffusive than the original scheme while retaining the implicit character of the particular SWAN set-up. The additional computational burden of the stationary alternative scheme is negligible, and the expense of the nonstationary alternative scheme is comparable to those used by other third generation wave models. To further accommodate large-scale applications of SWAN, the model is reformulated in terms of spherical coordinates rather than the original Cartesian coordinates. Thus the modified model can calculate wave energy propagation accurately and efficiently at any scale varying from laboratory dimensions (spatial scale O(10 m) with resolution O(0.1 m)), to near-shore coastal dimension (spatial scale O(10 km) with resolution O(100 m)) to oceanic dimensions (spatial scale O(10 000 km) with resolution O(100 km). 相似文献
6.
Kern E. Kenyon 《Journal of Oceanography》1978,34(6):288-294
East-west vertical sections centered on Kinmei Seamount (35N, 172E) of potential temperature, salinity, and oxygen, based on recent standard hydrographic measurements, and vertical profiles ofin situ temperature and density (
4) east of the seamount, based on STD data, show contrasting variability in the deep water characteristics east and west of the seamount. These data are consistent with horizontal variations in water mass properties (temperature-salinity and temperature-oxygen curves) east of the seamount between 2,600–3,900 m but not west of the seamount. East of the seamount on surfaces of constant potential temperature (or density) salinity and oxygen are higher at a station 200 km from the seamount than at stations on either side. From these relations and from known deep water properties of the North Pacific, it is suggested that east of the seamount, between 2,600–3,900 m, the observations are consistent with northward flow, which is interpreted to be a western boundary current with an east-west scale of about 300 km. 相似文献
7.
《Ocean Modelling》2008,20(3):293-311
A diagnostic method for calculating physical and numerical mixing of tracers in ocean models is presented. The physical mixing is defined as the turbulent mean tracer variance decay rate. The numerical mixing due to discretisation errors of tracer advection schemes is shown to be the decay rate between the advected square of the tracer variance and the square of the advected tracer and can be easily implemented into any ocean model. The applicability of the method is demonstrated for four test cases: (i) a one-dimensional linear advection equation with periodic boundary conditions, (ii) a two-dimensional flat-bottom lock exchange test case without mixing, (iii) a two-dimensional marginal sea overflow study with mixing and entrainment and (iv) the DOME test case with a dense bottom current propagating down a broad linear slope. The method has a number of advantages over previously introduced estimates for numerical mixing. 相似文献
8.
为了了解海山富钴结壳中金属元素的来源及其形成环境,对中太平洋某海山周围两个站位(一个位于海山斜坡上部,另一个位于海山外围较远处)进行了海水水柱综合水化学分析,发现两个站位溶解氧、pH及营养盐的分布是一致的,反映了两个站位海水化学环境的相似性,而剖面上金属元素含量却存在很大差异,位于海山斜坡上部站位的金属元素含量明显高于离海山较远的站位,说明海山结壳的主要金属来源于海山当地的水岩反应甚至低温热液活动。尽管存在差异,但在两个不同站位均存在近底层金属元素含量高,这印证了通过势温分布推断的本区存在南极底层水(AABW)影响的判断,说明AABW在本研究区确实存在,并且是维持海山斜坡强氧化环境的主要因素,AABW可能同时起着输运部分成矿元素的作用,但两个站位水柱金属元素含量的差异主要揭示了海山区存在水岩反应或者低温热液等当地物质的输入。 相似文献
9.
A number of parameterisations for the simulation of mixing processes in the thermocline are compared and tested against the microstructure data of the PROVESS campaigns, conducted in the northern part of the North Sea during the autumn of 1998. The transport term in the turbulent kinetic energy equation is parameterised via the introduction of a third stability function Sk for turbulent energy diffusion. The formulations are compared with a simpler scheme based upon limiting conditions for turbulence variables. Improved results are obtained with a new form of Sk. The best agreement is, however, found with the simpler limiting scheme. This is explained in terms of a turbulence length scale theory for stably stratified turbulence. In agreement with previous laboratory and ocean data it is found that the ratios of the Thorpe and Kolmogorov scales to the Ozmidov length scale approach critical limiting values in the thermocline. The first of these conditions is satisfied when limiting conditions are implemented into the scheme, providing the necessary minimum value for the dissipation rate, whereas the schemes without limiting conditions fail to produce this critical ratio. The basic reason for this failure is that the Thorpe scale is overestimated, which is shown to be connected to an even larger overprediction of the dissipation rate of temperature variance. To investigate the impact of non-resolved advective processes and salinity stratification on the turbulence predictions, additional numerical experiments were conducted using a simple scheme for data assimilation. The best agreement is found again with the limiting scheme, which is able to make reasonable predictions for the dissipation rate without knowing the detailed shape of the mean stratification profile. It is shown that advective transport due to tidally and wind-driven motions has a non-negligible impact on vertical mixing. This is seen in the data and the models by periodic enhancements of turbulent mixing inside the thermocline. 相似文献
10.
针对遥感资料与实况观测融合重构三维海温场的问题，改进了最优插值中的先验统计信息估计，并研究了背景场和观测项的各自影响机制。在最优插值中，将背景场分别取为平均气候场（静态方案）和遥感合成场（动态方案）；在最优融合前，用后验诊断方法迭代优化了背景误差和观测误差协方差；融合完成后，用观测空间诊断误差和模式格点指标对比分析两种方案。主要结论:（1）动态方案相对于静态方案分析误差减小的绝对量值由二者的观测误差之差决定、减小的相对程度由二者的背景误差之比决定；（2）背景场的调整作用在中高纬占优势、在赤道海域与观测项调整作用相当，是由协方差相关尺度的准纬向分布特征决定的；（3）动态分析场的中尺度信号谱能量整体比静态分析场高1~3个量级，但在热带海域相当；（4）遥感资料通过分辨实况观测所无法分辨出来的海温中尺度特征，达到减小误差、提高有效分辨率的效果。 相似文献