卡门涡街的细胞自动机模拟     

陈炬桦  邹秀芬 《华东地质学院学报》1995,18(4):361-365

本文介绍了细胞自动机模型，九点格子Ｂｏｌｔｚｍａｎｎ方法和正六边形格子Ｂｏｌｔｚｍａｎｎ方法，研究了一个基于九点格子方法的卡门涡街问题，得到了满意的结果。  相似文献   

氯化镁及其水合物的标准溶解焓与生成焓     

翟宗玺 《盐湖研究》1993,(1)

利用精密量热仪测定了MgCl_2、MgCl_2·2H_2O、MgCl_2·4H_2O和MgCl_2·6H_2O在298.15°K溶于水的积分溶解热,并利用Pitzer电解质溶液的。~ΦL方程,计算了溶质的相对表观摩尔热焓,从而得到标准溶解焓分别为(KJ·mol~(-1))—155.86±0.17、—79.45±O.17,—41.78±O.18和—14.58±0.16;晶格能分别为—2490.36,—3158.37,—3772.70和—4376.56。二、四、六水合物的标准生成焓分别为—1289.39,—1898.72和—2497.58;水合焓分别为—76.41,—114.08和—141.28。  相似文献   

Evaluation of ferrous and ferric Mössbauer fractions. Part II     

S.G. Eeckhout  E. De Grave 《Physics and Chemistry of Minerals》2003,30(3):142-146

Mössbauer fractions f are reported for various ferrous- and/or ferric-containing oxides, hydroxides, silicates, and phosphates to extend the list previously reported by De Grave and Van Alboom (1991). The f fractions were evaluated from the experimental temperature dependencies of their center shifts, assuming the Debye model for the lattice vibrations. For most Fe²⁺ sites the characteristic Mössbauer or lattice temperatures Θ_M are in the range 300–400 K, while those for Fe³⁺ sites are close to or exceed 500 K, implying significantly higher f fractions for Fe³⁺ than for Fe²⁺, in particular at room temperature. A correlation between Θ_M and the coordination type, or, for a given valence state and coordination type, between Θ_M and the mineral type is, however, not obvious.  相似文献   

Calculating the effective permeability of sandstone with multiscale lattice Boltzmann/finite element simulations     

Joshua A. White  Ronaldo I. Borja  Joanne T. Fredrich 《Acta Geotechnica》2006,1(4):195-209

The lattice Boltzmann (LB) method is an efficient technique for simulating fluid flow through individual pores of complex porous media. The ease with which the LB method handles complex boundary conditions, combined with the algorithm’s inherent parallelism, makes it an elegant approach to solving flow problems at the sub-continuum scale. However, the realities of current computational resources can limit the size and resolution of these simulations. A major research focus is developing methodologies for upscaling microscale techniques for use in macroscale problems of engineering interest. In this paper, we propose a hybrid, multiscale framework for simulating diffusion through porous media. We use the finite element (FE) method to solve the continuum boundary-value problem at the macroscale. Each finite element is treated as a sub-cell and assigned permeabilities calculated from subcontinuum simulations using the LB method. This framework allows us to efficiently find a macroscale solution while still maintaining information about microscale heterogeneities. As input to these simulations, we use synchrotron-computed 3D microtomographic images of a sandstone, with sample resolution of 3.34 μm. We discuss the predictive ability of these simulations, as well as implementation issues. We also quantify the lower limit of the continuum (Darcy) scale, as well as identify the optimal representative elementary volume for the hybrid LB–FE simulations.  相似文献   

Turbulence Structure in the Wake Region of a Meteorological Tower   总被引：2，自引：0，他引：2  

Christian Barthlott  Franz Fiedler 《Boundary-Layer Meteorology》2003,108(1):175-190

A meteorological tower significantly modifies the air flow, the mean windspeed and wind direction as well as the turbulencestructure of the air. Suchchanges can be noticed in particular in the wake region of the tower.Measurementson the 200 m tower ofForschungszentrum Karlsruhewere carried outusing Solent sonic anemometers in the lee of the towerand cup anemometers on both sides.In the wake region, spectral energydensity is increased in the high-frequency range. Superposition of this disturbance spectrum on the undisturbedspectrum yields a `knee' in the resulting spectrum. In the case of low turbulence intensity with stable stratification,a plateau with a constant energy content is observed in front of the knee.This effect is caused by the new production of turbulence energy from the mean flow as well as by an energy transfer fromlarger to smaller vortices. Power spectra in strongly stable conditionsshow a more rapid decrease of intensity in the region where the inertialsubrange is expected.The relevant scales of wake turbulence are derived from the maximum of the disturbance spectrum.Locations of the high-frequency peak do not depend on atmospheric stability,but are controlled mainly by mean wind speed.Apart from the reduction of the mean wind speed, the spectra and cospectra exhibit a strong anisotropy for such cases.The results demonstrate the significant influence of a tower on turbulence spectra in the wake region.  相似文献   

High-temperature deformation in the Neoproterozoic transpressional Ribeira belt, southeast Brazil     

Marcos Egydio-Silva  Alain Vauchez  Jrme Bascou  Joo Hippertt 《Tectonophysics》2002,352(1-2)

The Neoproterozoic Ribeira belt is subdivided in two domains with contrasting tectonic characteristics. The northern domain is dominated by shallowly dipping foliations and orogen-normal thrust tectonics. The southern domain is characterized by a 1000-km-long network of anastomosing transcurrent shear zones parallel to the belt. This contrast is interpreted as reflecting continent–continent convergence that is almost orthogonal to the margins in the northern domain and significantly oblique in the southern domain. The central, transitional, domain of the Ribeira belt displays the northern termination of the transcurrent shear zone network: the Além Paraíba–Pádua shear zone system (APPSS). The 250-km-long Além Paraíba–Pádua system involves granulites facies mylonites deformed through transpression.A detailed study of the microstructure and lattice preferred orientation (LPO) of the rock-forming minerals in these granulite mylonites allow a better understanding of deformation mechanisms active at high temperature in the crust. Plagioclase crystals are plastically deformed; they display curved twins and cleavages, mechanical twins, and evidence of dynamic recrystallization. LPO of plagioclase is consistent with activation of the (010) [100] and (010) [001] slip systems. LPO of orthopyroxene and amphibole indicates that these minerals have been deformed through dislocation creep with the activation of the (100) [001] slip system. Quartz in granulite mylonite displays evidence of extensive growth through grain boundary migration. The LPO of quartz is therefore the result of a static transformation of an initial, syn-kinematic LPO, and cannot be straightforwardly interpreted in terms of deformation mechanisms active during mylonitization.  相似文献   

Tectonometamorphic evolution of the Koralm Complex (Eastern Alps): constraints from microstructures and textures of the ‘Plattengneis’ shear zone     

Walter Kurz  Harald Fritz  Veronika Tenczer  Wolfgang Unzog 《Journal of Structural Geology》2002,24(12)

Lattice preferred orientations (LPO) of quartz have been investigated along a south–north oriented section across the Plattengneis of the Koralm Complex (Eastern Alps). The Plattengneis forms an important shear zone within the Austroalpine nappe complex of the Eastern Alps, which has developed during the Cretaceous evolution of the Alpine orogen. The quartz c-axes form small circle distributions in the southernmost parts of the Koralm Complex, which represent the uppermost structural level of the Plattengneis. Further to the North two maxima between the Y and Z directions of the finite strain can be interpreted in terms of preferred slip on the rhomb planes. These fabrics continuously grade into (type I and type II crossed) girdle distributions in a northward direction. A strong maximum near the Y-axis with the tendency to be distributed along a single girdle, with three corresponding maxima of a-axes near the margin of the pole figure, can be observed in the central and northern parts. Such LPO are characteristic for both high grade metamorphic conditions and high finite strain. The microstructures display that the deformation within the Plattengneis shear zone was synmetamorphic. A continuous increase of peak temperatures (and pressure) from approximately 550 °C to approximately 750 °C from the South to the central parts can be inferred from geothermometric calculations. The temperatures then decrease to approximately 650 °C from the central parts to the North. The related pressures increase from 8 to 16 kbar, and then decrease to 10 kbar. The LPO changes that have been observed in the study area are best interpreted in terms of temperature dependence of the activation of glide systems within quartz aggregates. The temperature and pressure evolution may indicate that the central parts of the Koralm Complex have been exhumed by larger amounts than the northern and southern parts. This is also documented by the LPO evolution. Therefore, we assume that the Plattengneis shear zone formed during the exhumation of the Koralm Complex, and is related to the exhumation of high-pressure units in the footwall of this shear zone. Accordingly, the kinematics of the Plattengneis shear zone is rather extensional than thrust-related. The implications for the structural evolution of the Eastern Alps are shortly discussed.  相似文献   

Cation ordering in omphacite and effect on deformation mechanism and lattice preferred orientation (LPO)   总被引：1，自引：0，他引：1  

Frank E. Brenker  Dave J. Prior  Wolfgang Friedrich Müller 《Journal of Structural Geology》2002,24(12)

We present microstructural data and lattice preferred orientations (LPOs) of omphacites from a suite of eclogites, from the Adula/Cima Lunga nappe (Central Alps). Our work shows a surprisingly strong correlation between the measured LPO and the ordering state of cations in omphacite. Estimates of deformation temperature from metamorphic petrology, together with measured omphacite compositions and LPOs, determine the field (ordering state), on the omphacite phase diagram, into which each sample falls. LPOs dominated by L-type and S-type signatures are developed in samples that fall in the P2/n field (ordered structure) and C2/c field (disordered structure), respectively.Dislocations with b=1/2−110 or b=[001] are observed in the transmission electron microscope (TEM) in all samples. The former change from a perfect dislocation in the C2/c structure to a partial in P2/n. Any movement of a partial dislocation requires the formation or growth of a stacking fault. Furthermore, in order to pass an obstacle a partial dislocation has to constrict to a unit dislocation. The energy to form a constriction is high in omphacite due to the large separation width. Thus, the activity of the b=1/2−110 dislocation is hindered in the P2/n structure relative to the C2/c structure, which change the balance between the two and might give rise to the different LPOs.  相似文献   

Continuation of the San Andreas fault system into the upper mantle: Evidence from spinel peridotite xenoliths in the Coyote Lake basalt, central California     

Sarah J. Titus  L. Gordon Medaris  Jr.  Herbert F. Wang  Basil Tikoff 《Tectonophysics》2007,429(1-2):1-20

The Coyote Lake basalt, located near the intersection of the Hayward and Calaveras faults in central California, contains spinel peridotite xenoliths from the mantle beneath the San Andreas fault system. Six upper mantle xenoliths were studied in detail by a combination of petrologic techniques. Temperature estimates, obtained from three two-pyroxene geothermometers and the Al-in-orthopyroxene geothermometer, indicate that the xenoliths equilibrated at 970–1100 °C. A thermal model was used to estimate the corresponding depth of equilibration for these xenoliths, resulting in depths between 38 and 43 km. The lattice preferred orientation of olivine measured in five of the xenolith samples show strong point distributions of olivine crystallographic axes suggesting that fabrics formed under high-temperature conditions. Calculated seismic anisotropy values indicate an average shear wave anisotropy of 6%, higher than the anisotropy calculated from xenoliths from other tectonic environments. Using this value, the anisotropic layer responsible for fault-parallel shear wave splitting in central California is less than 100 km thick. The strong fabric preserved in the xenoliths suggests that a mantle shear zone exists below the Calaveras fault to a depth of at least 40 km, and combining xenolith petrofabrics with shear wave splitting studies helps distinguish between different models for deformation at depth beneath the San Andrea fault system.  相似文献   

Lattice-preferred orientation of olivine found in diamond-bearing garnet peridotites in Finsch,South Africa and implications for seismic anisotropy     

《Journal of Structural Geology》2015

Seismic anisotropy in the upper mantle provides important constraints on mantle dynamics, continental evolution and global tectonics and is believed to be produced by the flow-induced lattice-preferred orientation (LPO) of olivine. Recent experimental studies at high pressure and temperature have suggested that the LPO of olivine is affected by pressure in addition to water and stress. However, there has been no report yet for the pressure-induced LPO of natural olivine because samples from the deep upper mantle are rare and often unsuitable for study due to ambiguous foliation and lineation. Here we show evidence of the pressure-induced LPO of natural olivine in diamond-bearing garnet peridotites from Finsch, South Africa. We found that the [010] axes of olivine are aligned subnormal to foliation and that the [001] axes are aligned subparallel to lineation, which is known as B-type LPO of olivine. The equilibrium pressure of the samples, as estimated using geobarometer, was greater than 4 GPa, indicating that the samples originated from a depth greater than ∼120 km. In addition, FTIR spectroscopy of the olivine showed that the samples are dry, with a water content of less than 90 ± 20 ppm H/Si (5.5 ± 1.2 ppm wt. H₂O). These data suggest that the samples are the first natural examples of olivine displaying B-type LPOs produced due to high pressure under dry condition. Our data indicate that the trench-parallel seismic anisotropy observed in many subduction zones in and below subducting slabs at depths greater than ∼90 km under dry condition may be attributed to the pressure-induced olivine fabrics (B-type LPO) and may be interpreted as the entrainment of the sub-lithospheric mantle in the direction of subduction rather than anomalous trench-parallel flow.  相似文献