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排序方式: 共有148条查询结果,搜索用时 31 毫秒
11.
Takashi Minoshima Yosuke Matsumoto Takanobu Amano 《Journal of computational physics》2011,230(17):6800-6823
We present a new numerical scheme for solving the advection equation and its application to Vlasov simulations. The scheme treats not only point values of a profile but also its zeroth to second order piecewise moments as dependent variables, for better conservation of the information entropy. We have developed one-and two-dimensional schemes and show that they provide quite accurate solutions within reasonable usage of computational resources compared to other existing schemes. The two-dimensional scheme can accurately solve the solid body rotation problem of a gaussian profile for more than hundred rotation periods with little numerical diffusion. This is crucially important for Vlasov simulations of magnetized plasmas. Applications of the one- and two-dimensional schemes to electrostatic and electromagnetic Vlasov simulations are presented with some benchmark tests. 相似文献
12.
陆相断陷湖盆陡坡带发育各种成围的砂砾岩扇体,其储集性能具有极强的非均质性,已成为高成熟勘探区重要的勘探目标,钻前对有利沉积相带的预测以及钻后对储集性能的分析,已成为提高勘探开发效益的关键.针对胜利油田济阳坳陷陡坡带发育的各种成围的砂砾岩扇体,综合应用测井相、多种测井咱应交会法、储层参数的测井定量解释、含油渗透层的测井判识等多种技术和方法,有效地对砂砾岩扇体的成围类型和储层岩性进行了判识,建立了孔隙度、渗透卑等储层参数解释的理论模型并进行了定量解释,划分了有效渗透层,取得了明显的勘探开发效果.这些新技术的综合运用为其他类似地区砂砾岩扇体的勘探与开发提供了技术支持. 相似文献
13.
14.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(5):1338-1346
Properties of obliquely propagating ion-acoustic solitons and double layers in a magnetized auroral plasma composed of hot adiabatic ions and two types of, cool and hot Maxwellian electrons are studied using Sagdeev pseudo-potential technique and assuming the quasi-neutrality condition. The new and surprising result which emerges from the model is that in contrast to the case of cold ions where ion-acoustic solitons and double layers are found for subsonic Mach numbers only, the hot ions case allows these nonlinear structures to exist for both subsonic and supersonic Mach number regimes. The double layers exist at lower angle of propagation as hot ion temperature is increased. The soliton electric field amplitudes are increased but their width and pulse duration are decreased with the increase in hot ion temperature. For the auroral zone parameters, the maximum electric field amplitude, width, pulse duration and speed for the solitons come out to be in the range ∼ (0.3–15) mV/m, ∼ (195–455) m, (7–20) ms and (22–26) km/s, respectively. The results seem to be in agreement with the Viking satellite observations in the auroral zone. 相似文献
15.
JieLi J.A.M.Kuipers 《中国颗粒学报》2004,2(1):1-12
The occurrence of heterogeneous flow structures in gas-particle flows seriously affects the gas-solid contacting and transport processes in high-velocity gas-fluidized beds. Particles do not disperse uniformly in the flow but pass through the bed in a swarm of clusters. The so-called “core-annulus“ structure in the radial direction and “S“ shaped axial distribution of solids concentration characterize the typical flow structure in the system. A computational study, using the discrete particle approach based on molecular dynamics techniques, has been carried out to explore the mechanisms underlying formation of the clusters and the core-annulus structure. Based on energybudget analysis including work done by the drag force, kinetic energy, rotational energy, potential energy, and energy dissipation due to particle-particle and particle-wall collisions, the role of gas-solid interaction and inelastic collisions between the particles are elucidated. It is concluded that the competition between gas-solid interaction and particle-particle interaction determines the pattern formation in high-velocity gas-solid flows: if the gas-solid interaction (under elevated pressure) dominates, most of particle energy obtained by drag from the gas phase is partitioned such that particle potential energy is raised, leading to a uniform flow structure. Otherwise, a heterogeneous pattern exists, which could be induced by both particle -particle collisions and gas-solid interaction. Although both factors could cause the flow instability, the non-linear drag force is demonstrated to be the necessary condition to trigger heterogeneous flow structure formation. As gas velocity increases and goes beyond a critical value, the fluid-particle interaction suppresses particle collisional dissipation, and as a consequence a more homogeneous flow regime is formed. 相似文献
16.
Teymuraz Abbasov 《中国颗粒学报》2007,5(1):71-83
This study is devoted to the explanation of different characteristics of magnetic filtration and the way these characteristics affect the important filtration parameters. Magnetic fields in pores and the force effect of these fields on magnetic particles and the magnetization properties of packed beds composed of ferromagnetic spheres and metal chips are evaluated. The profile of accumulation and capture regions of the particles, the variation of the fluid velocity in these regions and analytic expressions of particle capture radius are presented. The effects of filtration regime parameters on magnetic filter performance were investigated. An analytical expression has been obtained for the dependence of the logarithmic efficiency coefficient on filtration velocity, the geometry of filter elements, the particle size and other parameters of filtration. The stationary and non-stationary equations of the magnetic filtration processes are given. An expression of magnetic filter performance is shown with dimensionless parameters obtained from the filtration system. These relations are useful for calculations in engineering practice, including the design of magnetic filters, provision of suggestions on construction, and optimization and control of filter operation. 相似文献
17.
J. M. P. Q. Delgado 《Heat and Mass Transfer》2006,42(4):279-310
The phenomenon of dispersion (transverse and longitudinal) in packed beds is summarized and reviewed for a great deal of information
from the literature. Dispersion plays an important part, for example, in contaminant transport in ground water flows, in miscible
displacement of oil and gas and in reactant and product transport in packed bed reactors. There are several variables that
must be considered, in the analysis of dispersion in packed beds, like the length of the packed column, viscosity and density
of the fluid, ratio of column diameter to particle diameter, ratio of column length to particle diameter, particle size distribution,
particle shape, effect of fluid velocity and effect of temperature (or Schmidt number). Empirical correlations are presented
for the prediction of the dispersion coefficients (D
T and D
L) over the entire range of practical values of Sc and Pem, and works on transverse and longitudinal dispersion of non-Newtonian fluids in packed beds are also considered. 相似文献
18.
Pulsatile flow of a viscous fluid between two permeable beds is analyzed. The flow between and through the permeable beds are governed by the Navier-Stokes equations and Darcy's law, respectively. The velocity field and the volume flux are obtained for several cases and discussed. Further, when the permeability parameter k→0, the results agree with those of Wang (J. Appl. Mech. 38 (1971) 553). 相似文献
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20.
Luis M. Romeo Luis I. DíezIsabel Guedea Irene BoleaCarlos Lupiáñez Ana GonzálezJavier Pallarés Enrique Teruel 《Experimental Thermal and Fluid Science》2011,35(3):477-484
Oxyfuel combustion is a promising alternative for CO2 capture. While this has been proven in pulverized fuel (PF) burners, research in fluidized bed (FB) reactors is still scarce. Our work aims to increase the knowledge about this technology. To this purpose, a 95 kWth FB oxyfuel combustion test rig has been erected. Its main characteristics are described in this paper, giving detailed information on the subsystems: the FB reactor, the fuel and oxidant supplies, and ancillaries. Plant flexibility is emphasized. It allows to operate under different CO2/O2 ratios, and to recycle CO2 from the flue gases. Both the processes design and monitoring are supported by simulations that have been validated against experimental data, regarding fluid dynamics, combustion, and heat transfer. Finally, the performance of the facility has been tested both with coal alone and blended with biomass. CO2 concentrations over 90% (dry basis) in the flue gases have been obtained. Comparison of air and oxygen combustion tests and operational recommendations are discussed, confirming the feasibility of the FB oxyfuel technology for CO2 capture purposes. 相似文献