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71.
传统的U型通风工作面上隅角瓦斯积聚现象经常出现,严重制约着矿井正常生产能力的有效发挥,对矿井安全生产造成重大威胁。基于前人对采空区非均质多孔介质气体运移理论的研究,采用Fluent软件数值模拟研究了U型和上隅角埋管条件下U型通风系统的静压力场和瓦斯浓度场。研究结果表明:在相同的模型参数条件下,U型通风容易造成上隅角瓦斯积聚,上隅角瓦斯超限问题十分严重;采空区5m处埋管,治理上隅角瓦斯积聚的效果欠佳,达不到安全开采的条件;15m处埋管可以较好的解决上隅角瓦斯超限问题,工作面没有出现瓦斯积聚现象,工作面和回风巷的瓦斯浓度始终处于1%以下;25m处埋管的效果与15m基本相同,没有表现出更好的瓦斯治理效果。综合数值模拟的结果,确定了上隅角埋管抽放采空区瓦斯的理想抽放位置为距离地板垂高1.2m、沿走向深入采空区15m处。 相似文献
72.
“一一·二四”海难渤海风场的数值模拟 总被引:6,自引:0,他引:6
用中尺度数值模式 MM5对 1999年 11月 24日烟台附近发生重大海难事故的渤海风场进行了数值模 拟,探讨了该次冷锋大风的风场特征和影响机制.结果表明:用90km的粗网格可以成功地模拟地面冷高压 与锋面的发展和移动,以及高空环流形势的演变.而通过30km细网格的模拟发现,在冷锋后的行星边界层 中.存在着一条宽度为 200 kin的中尺度强风带,最大风速位于 925hPa,它与高空的极锋急流并不相连;细 网格还模拟出了渤海中尺度低压的发展过程,它使近地面层大风的强度显著加强.模拟还表明,海陆差异对 近地面的风场分布有重要的影响,强风带移入渤海后,在渤海海域形成一个 200—300 km的中尺度强风 区.因此,采用具有较高分辨率的中尺度数值模式,对提高渤海大风的预报水平,避兔海难事故的发生更具 有重要意义. 相似文献
73.
Alexander Baklanov Alix Rasmussen Barbara Fay Erik Berge Sandro Finardi 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):43-60
The last decade progress in numericalweather prediction (NWP) modelling and studies of urbanatmospheric processes for providing meteorological data forurban air pollution forecasting is analysed on examples ofseveral European meteorological centres. Modern nested NWP models are utilising land-use databasesdown to 1 km resolution or finer, and are approaching thenecessary horizontal and vertical resolution suitable forcity scale. The recent scientific developments in the fieldof urban atmospheric physics and the growing availabilityof high-resolution urban surface characteristics datapromise further improvements of the capability of NWPmodels for this aim. A strategy to improve NWP data forthe urban air pollution forecasting is suggested. 相似文献
74.
从实验和数值分析两方面研究了C6Hl2N 4+Mg+KClO4+SrSO4反应系统的振荡燃烧现象,并对反应机理进行了深层次的分析.结果表明,振荡燃烧是由化学动力学的非线性反馈引起的,即:反应系统中镁的三相与氧气的相互竞争反应造成系统的非线性化学振荡燃烧.氧化剂和可燃剂的比值,以及频率调节剂等吸热物质可调节气相镁的生成速率,能有效地控制药剂的振荡频率.选取适当的控制参数,可以使反应按照预定的、安全的过程进行,避免爆燃的产生.本文的研究结果对化工、军事等领域的安全控制具有重要意义. 相似文献
75.
76.
C. B. Vreugdenhil 《Journal of the American Water Resources Association》2002,38(4):1083-1095
ABSTRACT: Over the last 20 years, our possibilities to model river flows numerically have increased enormously. In this paper, the question is addressed whether a more sophisticated model is always better than a simpler one. Increased detail, both in finer resolution and in physical processes taken into account, has its price in more computer time, higher data need, and perhaps more unknown coefficients to be calibrated. Moreover, uncertainty in actual physical conditions (e.g., bottom roughness), inflow and parameters remains, which may dominate the uncertainty of the results. Also, the questions asked by a decision maker may not always be very precise. For a schematic but relevant example, we show that a better model does not necessarily give more reliable results because some of the basic uncertainties remain. It is concluded that we should use the simplest model that will answer the question as to the accuracy needed, taking into account uncertainties in the data 相似文献
77.
Robert G. Traver Arthur C. Miller 《Journal of the American Water Resources Association》1993,29(5):767-776
ABSTRACT: This paper confirms the use of interpolated data to refine water surface profiles. Sources of error within these computations are due to truncation error, inaccuracies in geometric data, and improper modeling. Confirmation includes the development of an equation that models the effect of data measurement error on the computed water surface profile. A review of interpolation procedures includes a proposed method based upon geometric properties. 相似文献
78.
Gabor M. Karadi Raymond J. Krisek Manual Beahea 《Journal of the American Water Resources Association》1970,6(3):424-438
The basic theories and fundamental assumptions usually employed in the solution of unsteady groundwater flow problems are reviewed critically. The best known method of analysis for such problems is based on the Dupuit-Forchheimer approximation and leads to a nonlinear parabolic differential equation which is generally solved by linearization or numerical methods. The accuracy of the solution to this equation can be improved by use of a different approach which does not employ the Dupuit Forchheimer assumption, but rather is based on a semi-numerical solution of the Laplace equation for quasi-steady conditions. The actual unsteady process is replaced by a sequence of steady-state conditions, and it is assumed that the actual unsteady flow characteristics during a short time interval can be approximated by those associated with “average” steady state flow. The Laplace equation is solved by a semi-discretization method according to which the horizontal coordinate is divided into subintervals, while the vertical coordinate is maintained continuous. The proposed method is applied to a typical tile drainage problem, and, based on a comparison of calculated results with experimental data, the method is evaluated and practical conclusions regarding its applicability are advanced. 相似文献
79.
80.
火灾试验结果和模拟预测结果常能表达成关于时间变化的曲线,为定量描述两种随时间变化曲线间相符合的程度,引入误差分析的函数分析法。采用适合于低Mach数流修正的N-S方程描述烟气的输运过程,使用大涡模拟和Smagorinsky亚格子模型,对封闭空间内的火灾过程进行数值模拟;对其计算结果的分析表明,函数分析法能定量对模拟预测曲线与试验曲线间的差别进行描述,模是两曲线值大小的相对误差的度量,余弦是两曲线形状相似程度的度量。 相似文献