A linear Boltzmann equation to model wave scattering in the marginal ice zone   总被引：1，自引：0，他引：1  

Michael H. Meylan  Diane Masson   《Ocean Modelling》2006,11(3-4):417-427

We present a linear Boltzmann equation to model wave scattering in the Marginal Ice Zone (the region of ocean which consists of broken ice floes). The equation is derived by two methods, the first based on Meylan et al. [Meylan, M.H., Squire, V.A., Fox, C., 1997. Towards realism in modeling ocean wave behavior in marginal ice zones. J. Geophys. Res. 102 (C10), 22981–22991] and second based on Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136]. This linear Boltzmann equation, we believe, is more suitable than the equation presented in Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136] because of its simpler form, because it is a differential rather than difference equation and because it does not depend on any assumptions about the ice floe geometry. However, the linear Boltzmann equation presented here is equivalent to the equation in Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136] since it is derived from their equation. Furthermore, the linear Boltzmann equation is also derived independently using the argument in Meylan et al. [Meylan, M.H., Squire, V.A., Fox, C., 1997. Towards realism in modeling ocean wave behavior in marginal ice zones. J. Geophys. Res. 102 (C10), 22981–22991]. We also present details of how the scattering kernel in the linear Boltzmann equation is found from the scattering by an individual ice floe and show how the linear Boltzmann equation can be solved straightforwardly in certain cases.  相似文献   

A scanning electron microscope study of the effects of dynamic recrystallization on lattice preferred orientation in olivine     

Kyung-Ho Lee  Zhenting Jiang  Shun-ichiro Karato   《Tectonophysics》2002,351(4)

Effects of dynamic recrystallization on lattice preferred orientation (LPO) in olivine were investigated through the combination of two SEM-based techniques, electron backscattered diffraction (EBSD) technique for crystallographic orientation measurement and backscattered electron imaging (BEI) for dislocation observation. Samples are experimentally deformed olivine aggregates in simple shear geometry. In the sample deformed at T=1473 K and high stresses (480 MPa), only incipient dynamic recrystallization is observed along grain-boundaries. Orientations of these small recrystallized grains are more random than that of relict grains, suggesting an important role of grain-boundary sliding at this stage of recrystallization. In the sample deformed at T=1573 K and low stress (160 MPa), dynamic recrystallization is nearly complete and the LPO is characterized by two [100] peaks. One peak is located at the orientation subparallel to the shear direction and is dominated by grains with high Schmid factor. The other occurs at high angles to the shear direction and is due to the contribution from grains with low Schmid factor. Grains with high Schmid factor tend to have higher dislocation densities than those with low Schmid factor. Based on these observations, we identify two mechanisms by which dynamic recrystallization affects LPO: (1) enhancement of grain-boundary sliding due to grain-size reduction, leading to the modification of LPO caused by the relaxation of constraint for deformation; (2) grain-boundary migration by which grains with lower dislocation densities grow at the expense of grains with higher dislocation densities. Based on the deformation mechanism maps and stress versus recrystallized grain-size relation, we suggest that the first mechanism always plays an important role whereas the second mechanism has an important effect only under limited conditions.  相似文献   

格子Boltzmann方法地震波场模拟   总被引：3，自引：0，他引：3  

董桥梁  姚姚 《地球科学》1997,22(6):638-642

格子Ｂｏｌｔｚｍａｎｎ方法是细胞自动机在某些学科中的具体化和应用。它根据微观运动过程的某些基本特征建立简化的、时间和空间完全离散的动力学模型，这种模型的平行行为符合宏观的微分方程。  相似文献   

Directional dependence of P- and S-wave propagation and polarization in foliated rocks from the Kola superdeep well: Evidence from laboratory measurements and calculations based on TOF neutron diffraction   总被引：1，自引：0，他引：1  

T.I. Ivankina  H.M. Kern  A.N. Nikitin 《Tectonophysics》2005,407(1-2):25-42

We have measured P- and S-wave velocities on two amphibolite and two gneiss samples from the Kola superdeep borehole as a function of pressure (up to 600 MPa) and temperature (up to 600 °C). The velocity measurements include compressional (Vp) and shear wave velocities (Vs1, Vs2) propagating in three orthogonal directions which were in general not parallel to inherent rock symmetry axes or planes. The measurements are accompanied by 3D-velocities calculations based on lattice preferred orientation (LPO) obtained by TOF (Time Of Flight) neutron diffraction analysis which allows the investigation of bulk volumes up to several cubic centimetres due to the high penetration depth of neutrons. The LPO-based numerical velocity calculations give important information on the different contribution of the various rock-forming minerals to bulk elastic anisotropy and on the relations of seismic anisotropy, shear wave splitting, and shear wave polarization to the structural reference frame (foliation and lineation). Comparison with measured velocities obtained for the three propagation directions that were not in accordance with the structural frame of the rocks (foliation and lineation) demonstrate that for shear waves propagating through anisotropic rocks the vibration directions are as important as the propagation directions. The study demonstrates that proper measurement of shear wave splitting by means of two orthogonal polarized sending and receiving shear wave transducers is only possible when their propagation and polarization directions are parallel and normal to foliation and lineation, respectively.  相似文献   

Internal erosion in granular media: direct numerical simulations and energy interpretation          下载免费PDF全文

Luc Sibille  Franck Lominé  Philippe Poullain  Yacine Sail  Didier Marot 《水文研究》2015,29(9):2149-2163

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Boundary effects on the Soil Water Characteristic Curves obtained from lattice Boltzmann simulations     

《Computers and Geotechnics》2016

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Wind-driven, double-gyre, ocean circulation in a reduced-gravity, 2.5-layer, lattice boltzmann model     

钟霖浩  冯士德  罗德海  高守亭 《大气科学进展》2006,23(4):561-578

A coupled lattice Boltzmann （LB） model with second-order accuracy is applied to the reduced-gravity, shallow water, 2.5-layer model for wind-driven double-gyre ocean circulation. By introducing the secondorder integral approximation for the collision operator, the model becomes fully explicit. The Coriolis force and other external forces are included in the model with second-order accuracy, which is consistent with the discretization accuracy of the LB equation. The feature of the multiple equilibria solutions is found in the numerical experiments under different Reynolds numbers based on this LB scheme. With the Reynolds number increasing from 3000 to 4000, the solution of this model is destabilized from the anti-symmetric double-gyre solution to the subtropic gyre solution and then to the subpolar gyre solution. The transitions between these equilibria states are also found in some parameter ranges. The time-dependent variability of the circulation based on this LB simulation is also discussed for varying viscosity regimes. The flow of this model exhibits oscillations with different timescales varying from subannual to interannual. The corresponding statistical oscillation modes are obtained by spectral analysis. By analyzing the spatiotemporal structures of these modes, it is found that the subannual oscillation with a 9-month period originates from the barotropic Rossby basin mode, and the interarmual oscillations with periods ranging from 1.5 years to 4.6 years originate from the recirculation gyre modes, which include the barotropic and the baroclinic recirculation gyre modes.  相似文献   

Numerical modeling investigation on turbulent oscillatory flow over a plane rough bed composed by randomly arrayed particles   总被引：1，自引：0，他引：1  

ZHOU Zhibo  ZHANG Jinfeng  ZHANG Qinghe  LIU Run 《海洋学报(英文版)》2018,37(7):62-68

A three-dimensional numerical model is established to simulate the turbulent oscillatory boundary layer over a fixed and rough bed composed by randomly arrayed solid spheres based on the lattice Boltzmann method and the large eddy simulation model.The equivalent roughness height,the location of the theoretical bed and the time variation of the friction velocity are investigated using the log-fit method.The time series of turbulent intensity and Reynolds stress are also investigated.The equivalent roughness height of cases with Reynolds numbers of 1×10~4–6×10~4 is approximately 2.81 d(grain size).The time variation of the friction velocity in an oscillatory cycle exhibits sinusoidal-like behavior.The friction factor depends on the relative roughness in the rough turbulent regime,and the pattern of solid particles arrayed as the rough bed in the numerical simulations has no obvious effect on the friction factor.  相似文献   

晶体点阵参数最小二乘法计算程序     

陈蓉美 《湖南地质》1990,9(1):54-59

作者以最小二乘法理法导出了晶体点阵参数计算的公式,并顾及了X射线粉晶衍射图测定所引起的系统误差修正,从而得到点阵参数的最佳估值。以导出的公式为数学模型编制了PC-1500微机的扩展BASIC语言程序,可适用于各晶系点阵参数的计算,使用方便。  相似文献   

格子玻尔兹曼方法及其在大气湍流研究中的应用     

程雪玲  胡非  赵松年  姜金华 《地球科学进展》2007,22(3):249-260

文章的目的是对格子玻尔兹曼方法进行系统的介绍，格子玻尔兹曼方法(Lattice Boltzmann Method)的出现直接来源于20世纪60年代的元胞自动机(Cellular Automata)思想，而这一方法用于解决流动现象时，又可以追溯到19世纪的分子运动论，求解的是Boltzmann提出的玻尔兹曼输运方程，因此将这一方法称为格子玻尔兹曼方法，之前也被称为格子气自动机(Lattice Gas Automaton)。该方法多用于研究复杂现象，如材料晶体凝聚时的生长过程、城市土地利用的演化等方面。在20世纪70年代由Hardy、Pomeau和Pazzis建立了第一个用于研究流体运动的格子气自动机，此后，这一方法被广泛用来模拟各种流动问题，诸如二相流、孔隙介质中的渗流等，并根据这一方法开发了相应的商业软件PowerFlow。同时，格子玻尔兹曼方法由于其在微观水平描述运动的特点，成为研究湍流的一个很好的数值计算工具，特别是用其进行直接数值模拟(DNS)计算，成为继传统的差分法、有限体积法和谱方法之后的又一有力的手段。而作为大气运动的一个主要现象的大气湍流，比普通湍流更加复杂，在这里着重介绍了大气湍流的特点和应用格子玻尔兹曼方法模拟湍流的发展过程。  相似文献