基于二维浅水方程的滑坡体兴波数值模型          下载免费PDF全文

房克照  尹晶  孙家文  焦子峰 《水科学进展》2017,28(1):96-105

基于有限体积方法和结构化网格,建立了海底滑坡引起的波浪传播数值模型。模型控制方程为考虑了海床随时间变化的二维浅水方程。采用中心迎风格式计算控制体界面数值通量,采用线性重构技术、局部海床高程处理技术和全隐式离散底摩阻项,保证了格式的和谐性、守恒性和水深非负性,有效处理了海岸动边界问题。时间积分采用具有强稳定性质的二阶龙格-库塔方法（ssp RK）。针对滑坡体兴波经典算例开展数值模拟,将计算结果与解析解、实验结果及其他模型计算结果进行比较和分析。结果表明,对于所考虑的计算工况,模型能较合理地模拟滑坡兴波的产生、传播和爬高过程。  相似文献   

Small‐scale variability in surface moisture on a fine‐grained beach: implications for modeling aeolian transport     

Brandon L. Edwards  Steven L. Namikas 《地球表面变化过程与地形》2009,34(10):1333-1338

Small‐scale variations in surface moisture content were measured on a fine‐grained beach using a Delta‐T Theta probe. The resulting data set was used to examine the implications of small‐scale variability for estimating aeolian transport potential. Surface moisture measurements were collected on a 40 cm × 40 cm grid at 10 cm intervals, providing a total of 25 measurements for each grid data set. A total of 44 grid data sets were obtained from a representative set of beach sub‐environments. Measured moisture contents ranged from about 0% (dry) to 25% (saturated), by weight. The moisture content range within a grid data set was found to vary from less than 1% to almost 15%. The magnitude of within‐grid variability varied consistently with the mean moisture content of the grid sets, following an approximately normal distribution. Both very wet and very dry grid data sets exhibited little internal variability in moisture content, while intermediate moisture contents were associated with higher levels of variability. Thus, at intermediate moisture contents it was apparent that some portions of the beach surface could be dry enough to allow aeolian transport (i.e. moisture content is below the critical threshold), while adjacent portions are too wet for transport to occur. To examine the implications of this finding, cumulative distribution functions were calculated to model the relative proportions of beach surface area expected to be above or below specified threshold moisture levels (4%, 7%, and 14%). It was found that the implicit inclusion of small‐scale variability in surface moisture levels typically resulted in changes of less than 1% in the beach area available for transport, suggesting that this parameter can be ignored at larger spatial scales. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

A meshless method to simulate solute transport in heterogeneous porous media     

Paulo A. Herrera  Marco Massabó  Roger D. Beckie 《Advances in water resources》2009

We derive a meshless numerical method based on smoothed particle hydrodynamics (SPH) for the simulation of conservative solute transport in heterogeneous geological formations. We demonstrate that the new proposed scheme is stable, accurate, and conserves global mass. We evaluate the performance of the proposed method versus other popular numerical methods for the simulation of one- and two-dimensional dispersion and two-dimensional advective–dispersive solute transport in heterogeneous porous media under different Pèclet numbers. The results of those benchmarks demonstrate that the proposed scheme has important advantages over other standard methods because of its natural ability to control numerical dispersion and other numerical artifacts. More importantly, while the numerical dispersion affecting traditional numerical methods creates artificial mixing and dilution, the new scheme provides numerical solutions that are “physically correct”, greatly reducing these artifacts.  相似文献   

Seasonal and spatial changes in the zooplankton community of Kongsfjorden, Svalbard   总被引：1，自引：0，他引：1  

Wojciech Walkusz  Slawek Kwasniewski  Stig Falk-Petersen  Haakon Hop  Vigdis Tverberg  Piotr Wieczorek  & Jan Marcin Weslawski 《Polar research》2009,28(2):254-281

Seasonal changes in the zooplankton composition of the glacially influenced Kongsfjorden, Svalbard (79°N, 12°E), and its adjacent shelf were studied in 2002. Samples were collected in the spring, summer and autumn in stratified hauls (according to hydrographic characteristics), by means of a 0.180-mm Multi Plankton Sampler. A strong front between the open sea and the fjord waters was observed during the spring, preventing water mass exchange, but was not observed later in the season. The considerable seasonal changes in zooplankton abundance were related to the seasonal variation in hydrographical regime. The total zooplankton abundance during the spring (40–2010 individuals m⁻³) was much lower than in the summer and autumn (410–10 560 individuals m⁻³). The main factors shaping the zooplankton community in the fjord include: the presence of a local front, advection, the flow pattern and the decreasing depth of the basin in the inner fjord. Presumably these factors regulate the gross pattern of zooplankton density and distribution, and override the importance of biological processes. This study increased our understanding of seasonal processes in fjords, particularly with regard to the strong seasonal variability in the Arctic.  相似文献   

Test of the Louis scheme and COARE algorithm for friction velocity in different wind-sea/swell regimes     

GAO Zhiqiu  HU Wen  LIU Shaomin 《海洋学报(英文版)》2005,24(4):20-28

The Louis scheme and the COARE algorithm （version 3.0） are tested against eddy covariance and inertial dissipation methods for friction velocity estimates in different wind-sea/swell regimes. Atmospheric forcing data, tabulated by Donelan et al. （1997.J Phys Oceanog, 27：2087-2099）, were collected from a mast on the foredeck of a SWATH （small water-plane area, twin hull） ship in deep sea off the State of Virginia during the surface wave dynamics experiment. These data are representative of low to moderate wind regimes. The aerodynamic roughness length is determined by using the Charnock relationship. The intercomparison shows that the Louis scheme and the COARE algorithm underestimate the friction velocity by 6% and 3% respectively under pure wind sea conditions, 15% and 13% respectively under cross swell conditions, and 21% and 17% respectively under counter swell conditions. The analysis shows that these underestimations were caused by the method chosen to determine the aerodynamic roughness length because it significantly underestimates the aerodynamic roughness length. It is especially true under the cross swell and counter swell conditions.  相似文献   

用含高色散性Boussinesq方程模拟潜堤上的波浪变形     

刘忠波  张日向  陈兵 《海洋技术学报》2005,24(2):66-68,120

基于一种高阶Boussiensq方程(刘忠波等,2004),采用预报-校正格式的有限差分法对该方程进行了数值离散,建立了数值模型。针对动量方程中三阶项的差分形式,采用了迎风格式和五点格式。通过数值模拟常水深下不同周期波浪传播变形,指出迎风格式在计算小周期波浪时存在的问题。为进一步验证数值模型的适用性,模拟了淹没潜堤上的传播变形。从数值结果与实验值的对比结果上看,该数值模型能较好地模拟波浪变形,可用于模拟实际中的波浪场问题。  相似文献   

循环同化相控阵雷达数据模拟对流触发同化方案研究     

龚澎  明杰  吕迎辉  张强 《气象科学》2024,44(1):115-124

利用WRF-EnKF同化系统,以2020年7月5日北京大兴发生的一次强对流天气背景下对流触发过程为个例,研究同化C波段相控阵雷达数据时更优的同化方案设置。本研究从同化频率、晴空数据处理阈值以及边界层杂波处理高度3个方面进行了研究。结果显示,高频同化可以抑制虚假回波,并有利于获得更准确的对流预报结果。将可靠晴空回波识别阈值设为-10 dBZ并剔除边界层内的低值回波可以有效改进对流触发的预报效果。为以后C波段相控阵雷达同化应用提供了新的同化方案思路。  相似文献   

惯导/双星定位组合导航方案与精度分析   总被引：4，自引：0，他引：4  

罗建军  袁建平 《全球定位系统》2005,30(2):41-46

分析了惯导／双星定位组合的可行性;针对惯导／双星定位组合导航在飞行器上应用存在的有关问题进行了讨论,提出了可能的对策。通过不同方案的比较分析,给出了较为实用的惯导／双星定位组合导航系统设计方案,并对组合的时机和组合导航的精度进行了仿真计算和结果分析。结果表明,采用按精度要求进行惯导／双星定位位置组合,可以在某种程度上弥补双星定位导航系统为有源系统的缺点,并具有较高的精度。  相似文献   

一个海气耦合模式模拟的云辐射过程   总被引：2，自引：0，他引：2  

汪方  丁一汇  徐影 《气象学报》2005,63(5):716-727

利用NCC/IAP T63海气耦合模式进行了20 a积分,详细分析了模式对云量及其辐射影响的模拟能力。结果表明,模式能够模拟出云量分布的基本特征,但同ISCCP卫星观测资料及ERA再分析资料相比还存在较大的差距,总体表现为模拟的云量偏小,尤其是海洋上部分地区出现了异常的低值区。通过对云量方案的改进,明显改善了两大洋东岸、夏半球副热带到中纬度海洋上空低云的模拟。但模式对热带印度洋到西太平洋地区云量的模拟仍然存在明显的偏差,这主要是由于模式对该地区强对流云模拟能力差,造成该地区高云模拟存在较大的误差。对辐射及其云辐射强迫的分析表明,模式对长波及其云辐射强迫的模拟要明显好于短波。短波辐射模拟的偏差主要是由于短波云辐射强迫模拟过小、耦合模式对积雪和海冰模拟较差、以及未考虑气溶胶的影响等原因共同引起的;而长波辐射模拟的差距主要是云量以及下垫面温度模拟不足造成的。相应于云量方案的改进,两大洋东岸、夏半球副热带到中纬度海洋上辐射(尤其是短波辐射)的模拟有了明显的改善,这也明显改进了这些地区的净辐射模拟。  相似文献   

Flood routing based on diffusion wave equation using mixing cell method     

V. P. Singh  Guang-Te Wang  D. D. Adrian 《水文研究》1997,11(14):1881-1894

A one-dimensional non-linear diffusion wave equation is derived from the Saint Venant equations with neglect of the inertia terms. This non-linear equation has no general analytical solution. Numerical schemes are therefore employed to discretize the space and time axes and convert the differential equation to difference form. In this study, the mixing cell method is used to convert the diffusion wave equation to difference form, in which the difference term can be eliminated by selecting an optimal space step size Δx when time step size Δt is given. When the time step size Δt→0, the space step size Δx=Q/(2S₀BC]_k) where Q is discharge, S₀ is bed slope, B is channel width and C_k is kinematic wave celerity, which is the same as the characteristic length proposed by Kalinin and Milyukov. The results of application to two cases show that the mixing cell and linear channel flow routing methods produce hydrographs that are in agreement with the observed flood hydrographs. © 1997 John Wiley & Sons, Ltd.  相似文献