共查询到17条相似文献，搜索用时 93 毫秒
1.
Modified PIC Method for Sea Ice Dynamics 总被引：1，自引：0，他引：1
The sea ice cover displays various dynamical characteristics such as breakup, rafting, and ridging under external forces. To model the ice dynamic process accurately, the effective numerical modeling method should be established. In this paper, a modified particle-in-cell （PIC） method for sea ice dynamics is developed coupling the finite difference （FD） method and smoothed particle hydrodynamics （SPH）. In this method, the ice cover is first discretized into a series of lagrangian ice particles which have their own sizes, thicknesses, concentrations and velocities. The ice thickness and concentration at Eulerian grid positions are obtained by interpolation with the Gaussian function from their surrounding ice particles. The momentum of ice cover is solved with FD approach to obtain the Eulerian cell velocity, which is used to estimate the ice particle velocity with the Gaussian function also. The thickness and concentration of ice particles are adjnsted with particle mass density and smooth length, which are adjusted with the redistribution of ice particles. With the above modified PIC method, numerical simulations for ice motion in an idealized rectangular basin and the ice dynamics in the Bohai Sea are carried out. These simulations show that this modified PIC method is applicable to sea ice dynamics simulation. 相似文献
2.
Considering the discontinuous characteristics of sea ice on various scales,a modified discrete element model（DEM） for sea ice dynamics is developed based on the granular material rheology.In this modified DEM,a soft sea ice particle element is introduced as a self-adjustive particle size function.Each ice particle can be treated as an assembly of ice floes,with its concentration and thickness changing to variable sizes under the conservation of mass.In this model,the contact forces among ice particles are calculated using a viscous-elastic-plastic model,while the maximum shear forces are described with the Mohr-Coulomb friction law.With this modified DEM,the ice flow dynamics is simulated under the drags of wind and current in a channel of various widths.The thicknesses,concentrations and velocities of ice particles are obtained,and then reasonable dynamic process is analyzed.The sea ice dynamic process is also simulated in a vortex wind field.Taking the influence of thermodynamics into account,this modified DEM will be improved in the future work. 相似文献
3.
Ice loads on a ship hull affect the safety of the hull structure and the ship maneuvering performance in ice-covered regions. A discrete element method （DEM） is used to simulate the interaction between drifting ice floes and a moving ship. The pancake ice floes are modelled with three-dimensional （3-D） dilated disk elements considering the buoyancy, drag force and additional mass induced by the current. The ship hull is modelled with 3D disks with overlaps. Ice loads on the ship hull are determined through the contact detection between ice floe element and ship hull element and the contact force calculation. The influences of different ice conditions （current velocities and directions, ice thicknesses, concentrations and ice floe sizes） and ship speeds are also examined on the dynamic ice force. The simulated results are compared qualitatively well with the existing field data and other numerical results. This work can be helpful in the shil3 structure design and the navigation securitv in ice-covered fields. 相似文献
4.
The mixing characteristics of particles such as dredged sediment of variable size discharged into cross flow are studied by a 3D numerical model, which is developed to model the particle-fluid two-phase flow. The Eulerian method with the modified k-ε parameterization of turbulence for the fluid phase is used to solve fluid phase, while a Lagrangian method for the solid phase (particles), both the processes are coupled through the momentum sources. In the model the wake turbulence induced by particles has been included as additional source term in the k-ε model; and the variable drift velocities of the particles are treated efficiently by the Lagrangian method in which the particles are tracked explicitly and the diffusion process is approximated by a random walk model. The hydrodynamic behavior of dumping a cloud of particles is governed by the total buoyancy of the cloud, the drag force on each particle and the velocity of cross-flow. The computed results show a roughly linear relationship between the displacement of the frontal position and the longitudinal width of the particle cloud. The particle size in the cloud and the velocity of cross flow dominate the flow behavior. The computed results are compared with the results of laboratory experiments and satisfactory agreement is obtained. 相似文献
5.
A viscoelastic-plastic constitutive model with Mohr-Coulomb yielding criterion for sea ice dynamics 总被引：2，自引：0，他引：2
A new viscoelastic-plastic （VEP） constitutive model for sea ice dynamics was developed based on continuum mechanics. This model consists of four components： Kelvin-Vogit viscoelastic model, Mohr-Coulomb yielding criterion, associated normality flow rule for plastic rehololgy, and hydrostatic pressure. The numerical simulations for ice motion in an idealized rectangular basin were made using smoothed particle hydrodynamics （SPH） method, and compared with the analytical solution as well as those based on the modified viscous plastic（VP） model and static ice jam theory. These simulations show that the new VEP model can simulate ice dynamics accurately. The new constitutive model was further applied to simulate ice dynamics of the Bohai Sea and compared with the traditional VP, and modified VP models. The results of the VEP model are compared better with the satellite remote images, and the simulated ice conditions in the JZ20-2 oil platform area were more reasonable. 相似文献
6.
基于高光谱遥感的渤海海冰厚度半经验模型 总被引：1，自引：0，他引：1
Sea ice thickness is one of the most important input parameters for the prevention and mitigation of sea ice disasters and the prediction of local sea environments and climates. Estimating the sea ice thickness is currently the most important issue in the study of sea ice remote sensing. With the Bohai Sea as the study area, a semiempirical model of the sea ice thickness(SEMSIT) that can be used to estimate the thickness of first-year ice based on existing water depth estimation models and hyperspectral remote sensing data according to an optical radiative transfer process in sea ice is proposed. In the model, the absorption and scattering properties of sea ice in different bands(spectral dimension information) are utilized. An integrated attenuation coefficient at the pixel level is estimated using the height of the reflectance peak at 1 088 nm. In addition, the surface reflectance of sea ice at the pixel level is estimated using the 1 550–1 750 nm band reflectance. The model is used to estimate the sea ice thickness with Hyperion images. The first validation results suggest that the proposed model and parameterization scheme can effectively reduce the estimation error associated with the sea ice thickness that is caused by temporal and spatial heterogeneities in the integrated attenuation coefficient and sea ice surface. A practical semi-empirical model and parameterization scheme that may be feasible for the sea ice thickness estimation using hyperspectral remote sensing data are potentially provided. 相似文献
7.
The Chukchi and Beaufort Seas include several important hydrological features： inflow of the Pacific water, Alaska coast current （ ACC ）, the seasonal to perennial sea ice cover, and landfast ice ＇along the Alaskan coast. The dynamics of this coupled ice-ocean system is important for both regional scale oceanography and large-scale global climate change research. A mumber of moorings were deployed in the area by JAMSTEC since 1992, and the data revealed highly variable characteristics of the hydrological environment. A regional high-resolution coupled ice-ocean model of the Chukchi and Beaufort Seas was established to simulate the ice-ocean environment and unique seasonal landfast ice in the coastal Beaufort Sea. The model results reproduced the Beaufort gyre and the ACC. The depthaveraged annual mean ocean currents along the Beaufort Sea coast and shelf hreak compared well with data from four moored ADCPs, but the simulated velocity had smaller standard deviations, which indicate small-scale eddies were frequent in the region. The model resuits captured the sea,real variations of sea ice area as compared with remote sensing data, and the simulated sea ice velocity showed an ahnost stationary area along the Beaufort Sea coast that was similar to the observed landfast ice extent. It is the combined effects of the weak oceanic current near the coast, a prevailing wind with an onshore component, the opposite direction of the ocean current, and the blocking hy the coastline that make the Beaufort Sea coastal areas prone to the formation of landfast ice. 相似文献
8.
北极海冰密集度预报对大气强迫敏感性的个例研究 总被引：3，自引：0，他引：3
YANG Qinghu LIU Jiping ZHANG Zhanhai SUI Cuijuan XING Jianyong LI Ming LI Chunhu ZHAO Jiechen ZHANG Lin 《海洋学报(英文版)》2014,33(12):15-23
A regional Arctic configuration of the Massachusetts Institute of Technology general circulation model （MIT-gcm） is used as the coupled ice-ocean model for forecasting sea ice conditions in the Arctic Ocean at the Na-tional Marine Environmental Forecasting Center of China （NMEFC）, and the numerical weather prediction from the National Center for Environmental Prediction Global Forecast System （NCEP GFS） is used as the atmospheric forcing. To improve the sea ice forecasting, a recently developed Polar Weather Research and Forecasting model （Polar WRF） model prediction is also tested as the atmospheric forcing. Their forecasting performances are evaluated with two different satellite-derived sea ice concentration products as initializa-tions： （1） the Special Sensor Microwave Imager/Sounder （SSMIS） and （2） the Advanced Microwave Scanning Radiometer for EOS （AMSR-E）. Three synoptic cases, which represent the typical atmospheric circulations over the Arctic Ocean in summer 2010, are selected to carry out the Arctic sea ice numerical forecasting experiments. The evaluations suggest that the forecasts of sea ice concentrations using the Polar WRF atmo-spheric forcing show some improvements as compared with that of the NCEP GFS. 相似文献
9.
A lot of tests on ice forces on vertical cylindrical piles are conducted in the ice basin of ice laboratory in Tianjin University to identify the characteristics of ice forces on fixed platforms in the Bohai Gulf. A function of ice forces is simplified on basis of test data, and the charateristics of the ice forces including the amplitude of the force and the breaking frequency of the ice sheet is detailed by use of the Fast-Fourier-Transform method. The results show that the ice breaking frequency presents a linear relationship with the ratio of ice moving velocity to ice thickness at low velocities. At high velocities, the frequency remains constant with the increase of the ratio of ice moving velocity to ice thickness. These conclusions are compared those published in literature. 相似文献
10.
11.
综合考虑欧拉坐标下有限差分法(FDM)在海冰动力学计算中的效率,以及拉格朗日坐标下光滑质点流体动力学方法(SPH)对海冰流变行为的精确模拟,本文发展了一种海冰动力学的混合拉格朗日-欧拉(HLE)数值方法。该方法首先在拉格朗日坐标下将海冰离散为若干个具有厚度、密集度的海冰质点,并由这些海冰质点通过Gauss函数对欧拉网格上的海冰参量进行积分插值;然后,在欧拉坐标下对海冰动量方程进行差分计算以确定各网格节点的海冰速度,并由此采用Gauss函数积分插值出拉格朗日坐标下各海冰质点的速度分布;最后,通过对海冰质点运动和分布的计算,确定出各海冰质点的位置、厚度和密集度等参量。采用该HLE方法对规则区域内的海冰堆积过程和涡动风场作用下的海冰动力演化趋势进行了数值试验;最后,采用该HLE方法对渤海海冰的动力过程进行了72h数值模拟,其计算结果与卫星遥感图像和现场观测资料吻合较好。以上计算结果均表明该HLE方法在海冰动力学数值模拟中具有较高的计算效率和模拟精度,可用于海冰动力过程的数值模拟。 相似文献
12.
冰动力学的拉格郎日离散元模式 总被引：5，自引：0，他引：5
本文描述一种应用于河冰和海冰动力学研究的平滑质点流体力学的离散元模式。该离散元方法是一种自由拉格郎日方法,和传统的欧拉网格数值方法相比,它具有较小的数值扩散并且能够更加灵活地处理复杂的冰过程等许多优点。本文首先给出海冰动力学的离散元模式的基本方法,并与欧拉有限差分方法和半拉格郎日的质点一网格方法进行了对比,其次,本文还给出了离散元海冰模式在渤海的一个应用。 相似文献
13.
海冰动力过程的改进离散元模型及在渤海的应用 总被引：1，自引：0，他引：1
海冰的断裂、重叠和堆积等离散分布特性广泛地存在于极区和副极区的不同海域,并对海冰的生消、运移过程有着重要影响。针对海冰在不同尺度下的离散分布特点,发展海冰动力过程的离散元方法有助于完善海冰数值模式,提高海冰数值模拟的计算精度。为此,本文针对海冰生消运移过程中的非连续分布和形变特性,发展了适用于海冰动力过程的改进离散元模型(MDEM)。不同于传统离散元方法,该模型将海冰离散为具有一定厚度、尺寸和密集度的圆盘单元。海冰单元设为诸多浮冰块的集合体,其在运移和相互接触碰撞过程中,依照质量守恒发生单元尺寸、密集度和厚度的相应变化。基于海冰离散性和流变性的特点,该模型采用黏弹性接触本构模型计算单元间的作用力,并依据Mohr-Coulomb准则计算海冰法向作用下的塑性变形及切向摩擦力。为验证该模型的可靠性,本文对海冰在规则水域内的运移和堆积过程进行了分析,离散元计算结果与解析值相一致;此外,对旋转风场下海冰漂移规律的模拟进一步验证了本文方法的精确性。在此基础上,对渤海辽东湾的海冰动力过程进行了48h数值分析,计算结果与卫星遥感资料和油气作业区的海冰现场监测数据吻合良好。在下一步工作中将考虑海冰离散元模拟中的热力因素影响,发展具有冻结、断裂效应的海冰离散元模型,更精确地模拟海冰动力-热力耦合作用下的生消和运移过程。 相似文献
14.
南大洋在全球气候系统中起着重要的作用,对世界大洋水团的形成有重要的影响。在世界大洋中,约有55%-60%的海水特性应当归结于南大洋的物理过程。目前,南大洋的研究已得到各国海洋学者的日益关注,进展较大。但是,对于地处印度洋扇形区的普里兹湾海区的观测和研究则相对较少,其结果的差别甚大。例如底层水形成问题,有些研究者认为这一海区的底层水主要来源于威德尔海和罗斯海,本区内对底层水的贡献即使有,也是非常小的(Smith et al.,1984; Mantyla et al.,1995)。而有些研究者则从观测资料中找到了底层水有可能形成的迹象。就目前研究的结果来看,有些年份,如1982年(Middleton et al.,1989),1987年(Woehler et al.,1988),1991年(乐肯堂等,1996)均发现了异常高盐的陆架水,它有可能与深层水混合而形成底层水。对于该海区的环流特别是深层环流迄今为止也是知之甚少。大多数研究是基于动力高度的计算结果( Grigor yev,1967;Smith et al.,1984,1993;Middleton et al.,1989),但他们给出的环流型式相互之间差异很大。这些差异的存在,虽然确有年际变化等因素,但也不能排除研究方法本身的局限。该海区地形复杂(图1),海冰有显著的季节变化和年际变化(Allison et al.,1993,1994),使得该海区的物理海洋状况非常复杂。南极地区由于环境恶劣,海洋观测集中在夏季,并且资料的连续性较差,因而使传统的研究方法受到很大限制。为了充分发挥有限的实测资料的作用,采用合理的动力学和热力学模式并利用数值方法求解模式方程,不失为一种有效的研究途径。迄今为止,这一海区的数值研究还很少,考虑热力学作用的模式则尚未见诸报道。本文将利用最新的资料和模式,并在模式中同时考虑动力学和热力学的作用,用以研究普里兹湾海区的环流与海冰的动力学和热力学过程。以往的研究发现、等密面分析是研究普里兹湾海区混合与环流的有效方法(乐肯堂等,1997),我们将采用国际上新近发展起来的一种基于等密面的数值计算模式,研究普里兹湾海区环流和海冰的季节变化。这一工作将有助于进一步解决该海区南极底层水的形成问题,因而对于深入认识该海区在南大洋环流系统以至全球气候系统中的作用有重要意义。 相似文献
15.
锥体导管架海洋平台冰激振动的DEM-FEM耦合分析及高性能算法 总被引：1，自引：0，他引：1
在寒区海域，冰荷载是影响海洋平台安全运行的主要环境荷载之一，由其引起的冰激振动给平台结构及其上部设备带来了严重危害。为分析不同冰况下平台的振动响应，本文建立了导管架海洋平台冰激振动的离散元（DEM）-有限元（FEM）耦合模型。采用具有黏接-破碎性能的等粒径球体离散单元对海冰的破碎特性进行模拟，通过由梁单元构建的海洋平台有限元模型获得结构的振动响应。在离散元与有限元的接触区域中实现了两个模型间计算参数的传递。为提高该耦合模型的计算效率和规模，发展了基于动力子结构方法的DEM-FEM耦合模型。为验证该耦合模型的有效性和可行性，将不同冰况下得到的冰荷载与ISO19906和JTS 144-1-2010标准进行了对比。结果表明，计算得到的冰荷载与标准相近，且冰厚与冰荷载呈二次非线性关系。同时，从冰速和冰厚两方面对比了渤海四桩腿JZ20-2 MUQ锥体导管架平台冰激振动加速度的数值结果和现场实测数据，发现冰速与振动加速度呈线性关系，冰厚与振动加速度呈二次非线性关系，并且振动加速度与冰速和冰厚平方的乘积呈线性关系。 相似文献
16.
Numerical simulation for dynamical processes of sea ice 总被引：1，自引：0，他引：1
ＮｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｆｏｒｄｙｎａｍｉｃａｌｐｒｏｃｅｓｓｅｓｏｆｓｅａｉｃｅＷｕＨｕｉｄｉｎｇ，ＢａｉＳｈａｎ，ＺｈａｎｇＺｈａｎｈａｉａｎｄＬｉＧｕｏｑｉｎｇ（ＲｅｃｅｉｖｅｄＭａｙ１６，１９９６；ａｃｃｅｐｔｅｄＪａｎｕａｒｙ... 相似文献
17.
《Ocean Modelling》2003,5(1):1-15
Modern numerical sea-ice models contain detailed parameterizations of dynamic and thermodynamic processes affecting ice distribution and thickness. However, nearly all such models advect sea ice in response to wind and ocean forcing using either upstream or centered-difference methods, whose deficiencies are well known. We describe application of the second-order moment advection scheme of Prather [J. Geophys. Res. 91 (1986) 6671]. In idealized tests this method produces relatively distinct ice edges while maintaining positive ice thicknesses and concentrations. Sensitivity of an Arctic circulation model forced by climatological data is described. 相似文献