人体降温服在矿井热环境中的应用综述

降温服是一种应用于高温环境条件下的个体防护设备。根据深矿井热害治理需求,提出用人体降温服对人体直接降温的个体防护方法。结合降温服的降温原理和分类,对个体降温服国内外研究现状及其在矿井热害治理中的可能应用进行了综述和评价分析。为在深矿井热害治理中有针对性的研究、设计和应用矿用人体降温服提供参考。     

Turbulent Ventilation of a Street Canyon

A selection of turbulence data corresponding to 185 days of field measurements has been analysed. The non-ideal building geometry influenced the circulation patterns in the street canyon and the largest average vertical velocities were observed in the wake of an unbroken line of buildings. The standard deviation of vertical velocity fluctuations normalised by the ambient wind speed was relatively insensitive to ambient wind direction and sensor position, and it was usually larger than the corresponding 1-hour average velocity. Cross-correlations of spatially separated velocity measurements were small, and this suggests that most of the velocity fluctuations were fairly local and not caused by unsteady street vortices. The observed velocities scaled with the ambient wind speed except under low-wind conditions.     

旋风分离器排气管最佳插入深度的实验与分析

采用实验方法考察物料特性、入口气速、排气管直径、入口截面积4种因素对排气管最佳插入深度的影响。实验结果表明,排气管的最佳插入深度主要受粉料中位粒径和粒径分布的影响,中位粒径越小,包含的小粒径颗粒越多,最佳插入深度越大,而与其他3项参数无关。另外,插入深度在最佳位置附近变化时,效率波动不大,远离最佳位置后,效率大幅下降,并且在大排气管直径,大入口条件下,效率对插入深度更为敏感。短路流和内旋流二次分离的协同作用是形成以上现象的主要原因。     

2019年辽宁开原龙卷风观测事实分析

利用加密自动站、FY-4A卫星及多普勒雷达等观测资料,对2019年7月3日辽宁开原突发龙卷天气进行分析.结果表明:在冷涡减弱阶段,中纬度冷空气活动频繁,冷涡底部500 hPa与850 hPa的短波槽垂直分布,利于辽宁北部对流不稳定加强.FY-4A可见光云图显示,开原龙卷生消迅速,有明显的上冲云顶.雷达反射率因子特征是,...     

瓦斯抽采钻孔棱状钻杆排渣原理数值模拟

为分析棱状类钻杆应用于松软突出煤层钻进存在优势的原因,基于流体力学理论,建立了棱状钻杆排渣模型,采用有限元方法,应用标准κ-ε模型方程进行计算,对钻杆旋转与周边流体相互作用的流场特征进行分析.结果表明,在钻杆棱角处形成“低压高速区”,棱边处形成“高压低速区”,钻杆棱边壁面流体产生速度、压力波动差,从而在“高压低速区”钻杆壁面形成强烈的“压差涡流”现象,减少了钻屑在孔底堆积致使钻孔堵塞的概率.应用棱状钻杆在松软突出煤层中施工钻孔,钻进深度提高34.6％,钻进效率提高21.1％,钻孔达标率由9.8％提高到48.3％,试验期间,钻杆强度可靠,未出现丢钻、断钻现象.     

Vertical Buoyant Jets in a Linearly Stratified Ambient Cross-Stream

In this study a numerical simulation is performed to investigate the effect of ambient density stratification on the characteristic of a vertical buoyant jet in a stably linearly stratified ambient cross-stream. Based on the ensemble integral method, the theoretical formulation for such a flow field consists of a set of elliptic Reynolds-averaged equations incorporating with the k– transport equations for the turbulence closure. An oscillating motion can be observed in the computed jet trajectory, and the corresponding alternative variation of dominant quantities for the induced momentum and buoyancy of the jet are examined by direct integration on a cross-section along the jet axis. The influences on the jet development both by the ambient cross-stream and the stratification are investigated. The oscillation characteristic shows that a linear relation holds between the wavenumber of jet trajectory, crossflow velocity and the Brunt–Väisälä frequency of ambient stratification. Computational results indicate that the formation of the secondary and a third pairs of vortices, which are not induced in the unstratified environment, causes the jet flow oscillation from its maximum height-of-rise in the flowing direction. The ambient stratification prohibits the growth of the plume radius and reduces the mixing rate as well as the plume rise. The developed flow indicates the transformation of entrainment mechanism in stratified crossflow.     

森林火灾旋涡机理初探

作者在热风洞中模拟森林火灾发生的环境条件，在可燃物中设置一突出的圆柱形钝体，发现在有风燃烧火焰流向钝体下游时，紧贴不可燃的壁面，存在两个剧烈燃烧的驻涡，并且涡可以一定的频率脱落，从现象上看与冷流体流动中的卡门涡街有相似的地方，也有完全不同之处。高温燃烧气体新构成的涡的存在，易使下游可燃物点燃，从而加速火蔓延速度。     

流体流动状态对超滤效率及膜污染的影响

超滤技术作为膜分离技术的一种,由于具有效率高、能耗低等优点已经被多种行业广泛应用.但是,浓差极化和膜污染却极大降低膜分离效率,成为制约膜分离技术推广应用的重要因素.解决和减轻浓差极化和膜污染的方法有很多,本文着重于流体流动状态对浓差极化和膜污染的影响进行了论述.     

Influence of Geometry on the Mean Flow within Urban Street Canyons – A Comparison of Wind Tunnel Experiments and Numerical Simulations

A comparison between numerical simulations and wind tunnel modelling has been performed to examine the variation with streamwise aspect ratio (width/height, W/H) of the mean flow patterns in a street canyon. For this purpose a two-dimensional (2-D) cavity was subjected to a thick turbulent boundary layer flow perpendicular to its principal axis. Five different test cases, W/H = 0.3, 0.5, 0.7, 1.0 and 2.0, have been studied experimentally with flow measurements taken using pulsed-wire anemometry. The results show that the skimming flow regime, with a large vortex in the canyon, occurred for all the cases investigated. For the cavities with W/H 0.7 a weaker secondary circulation developed beneath the main vortex. The narrower the canyon, the smaller the wind speed close to the cavity ground, giving increasingly poor ventilation qualities. The corresponding numerical results were obtained with the Computational Fluid Dynamics (CFD) code CHENSI that uses the standard k- model. The intercomparison showed good agreement in terms of the gross features of the mean flow for all the geometries examined, although some detailed differences were observed.     

The extraordinary events of the major,sudden stratospheric warming,the diminutive antarctic ozone hole,and its split in 2002

GOAL, SCOPE AND BACKGROUND: Great interest in the unprecedented events of the major, sudden stratospheric warming and the ozone hole split over Antarctica in September 25, 2002 motivates a necessity to analyze the current understanding on the dynamics, chemistry and climate impacts that are associated with both events. METHODS: Significant progress in the analysis of the observational data obtained, as well as successful development and application of dynamical modeling, which have been achieved very recently, create a basis for the first survey on the role of the major, sudden stratospheric warming observed in the southern hemisphere and its relationship to the diminutive Antarctic ozone hole and its break up into two parts. RESULTS AND DISCUSSION: Special attention has been paid to assessments of the causes of the major warming event and the future expectations concerning the stratospheric ozone depletion effect. Among the principal results is the fact that, as the polar vortex elongated, it became hydrodynamically unstable, and this insta-, bility affected the upper troposphere and stratosphere. During the major, sudden stratospheric warming, the middle stratospheric vortex split into two pieces; one piece rapidly mixed with extra vortex air, while the other returned to the pole as a much weaker and smaller vortex. The polar night jet was considerably weaker than normal, and was displaced more poleward than has been observed in previous winters, resulting from a series of wave events (propagated from the troposphere) that took place over the course of the winter. Finally, the relative ozone decrease (increase) in the eastern Antarctic is tightly associated with westerly (easterly) zonal wind anomalies near the southern tip of South America, and the unusual behavior of the ozone hole in 2002 therefore appears to be caused by great easterlies in this region. CONCLUSIONS: The main conclusion is that the southern polar vortex and the diminutive ozone hole split into two parts in September 2002, due to the prevalence of very strong planetary waves, led to the appearance of a major, sudden stratospheric warming. Although there is evidence that sea surface temperature anomalies contributed to the excitation of the quite strong planetary waves over Antarctica in 2002, there is not yet a widely approved mechanism supporting that. RECOMMENDATIONS AND OUTLOOK:The appearance of the near-record size of the 2003 ozone hole confirmed that the 'no-ozone-hole' episode observed in the year 2002 does not denote a recovery of the ozone layer. Despite the current successful attempts to get a sufficient understanding for the genesis of both extraordinary events, more observations and further modeling efforts are necessary to more reliably assess the contribution of various dynamic mechanisms to the recently observed tropo-stratospheric surprises.