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101.
102.
为适应风险因素不确定性、随机性及动态反馈性等特点,建立新型富水岩溶隧道涌水风险评价体系,提出1种基于云模型的模糊综合评价方法.选取5个1级指标、29个2级指标构建评价指标体系;综合层次分析、熵权与加权平均计算法合理分配各指标权重;利用云生成算法计算出云数字特征参数并生成足够数量的云滴;将方法应用于贵州省某隧道涌水风险评... 相似文献
103.
选取某城市L型综合管廊电缆舱为研究对象,采用FDS数值模拟软件研究了不同火源位置对L型管廊电缆火灾温度纵向衰减规律、烟气浓度分布规律及烟气危害性的影响。研究结果表明,L型廊道构型影响了不同火源位置的管廊电缆火灾最高温度纵向衰减的连续性,基于热边界层理论提出了适用于L型管廊的二维平面最高温度纵向衰减模型。基于峰宽时间计算了L型管廊火灾的烟气总危害性参数,不同火源位置的烟气危害性总在靠近管廊节点位置处最低。这些结果可对综合管廊的消防设计与火灾防控提供参考。 相似文献
104.
This work investigates the release and dispersion of volatile organic hydrocarbons, which may escape from external floating roof tanks (EFRT) during normal operation or in case of damage. The dispersion will be described using CFD simulations in close range of the EFRT where hazardous areas are assigned. The aim of this work is to investigate which events can lead to emissions in dangerous quantities and to estimate the corresponding likelihood with regard to explosion protection. An emission in hazardous amount is present if the lower explosion limit has been exceeded and if the extent of this emission is not too low. It is discussed in particular whether the used zoning of potentially explosive areas is conservative or over-conservative. 相似文献
105.
为研究坡度隧道内列车阻滞后的火灾烟气蔓延行为,利用火灾动力学模拟软件(FDS)建立盾构铁路隧道火灾模型和CRH6高速列车阻滞模型,隧道坡度分别为0%、1.0%、1.5%、2.0%、2.5%、3.0%、3.5%和4.0%,通过分析隧道内烟气、温度、能见度等特征参数的变化规律,研究坡度隧道内高温烟气的受力情况,探讨坡度变化对火灾烟气蔓延的作用机理。结果表明,坡度隧道内发生火灾,随着烟气的蔓延,隧道内形成沿坡度方向的烟囱效应力,使得烟气在火源两侧呈不对称分布。火源下游区域的高温烟气在火风压和烟囱效应的协同作用下蔓延速度比上游更快,下游烟气层分界中性面与隧道轴线平行,上游烟气层分界中性面呈现水平状态。有坡度的铁路隧道内发生火灾,建议向火源下游方向施加纵向机械通风,人员向火源的上游方向疏散逃生更安全。 相似文献
106.
两个相邻高建筑物周围的风环境 总被引:3,自引:0,他引:3
描述研究了建筑物周围人行道高度风速分布特征的风洞模拟实验。结果表明:在一个横风向宽度很大的高大建筑物的迎风面拐角附近,风速增大约1倍;而在建筑物的前方有风速的骤变区,这均形成严重的风环境问题。当用一通道将该建筑物分割成两个相邻建筑物时,上述两方面的风环境问题得到了有效的改善,且通道宽度与建筑物顺风向尺度之比的优化数值在18至24之间 相似文献
107.
低层大气中固体粒子运动及其物理模拟 总被引:14,自引:0,他引:14
对于大气边界层中的固体粒子的风致运动-较大粒子的蠕动跃动和较小粒子悬浮-的主要特征作了介绍,着重介绍了在悬浮粒子运动的物理模拟研究方面的一些成果;复杂地形物低层大气湍流会显地提高起尘速率并改变降尘量的分布;有一定我向厚度的风障除了屏蔽效应--即背风侧平均风速的减小--外,还滕了终进入空气的灰尘数量的“宏观吸附效应”;总结了模拟悬浮粒子运动的风洞实验所应遵循的相似性准则,并提出了模拟防尘风障的中的 相似文献
108.
Jason A. Roney Bruce R. White 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):7668-7685
Emissions from fugitive dust due to erosion of “natural” wind-blown surfaces are an increasingly important part of PM10 (particulate matter with sizes of 10 μm aerodynamic diameter) emission inventories. These inventories are particularly important to State Implementation Plans (SIP), the plan required for each state to file with the Federal government indicating how they will comply with the Federal Clean Air Act (FCAA). However, techniques for determining the fugitive dust contribution to over all PM10 emissions are still in their developmental stages. In the past, the methods have included field monitoring stations, specialized field studies and field wind-tunnel studies. The measurements made in this paper allow for systematic determination of PM10 emission rates through the use of an environmental boundary layer wind tunnel in the laboratory. Near surface steady-state concentration profiles and velocity profiles are obtained in order to use a control volume approach to estimate emission rates. This methodology is applied to soils retrieved from the nation's single largest PM10 source, Owens (dry) Lake in California, to estimate emission rates during active storm periods. The estimated emission rates are comparable to those obtained from field studies and lend to the validity of this method for determining fugitive dust emission rates. 相似文献
109.
Wind Tunnel Experiments and Numerical Simulation of Snow Drifting around an Avalanche Protecting Dam
To learn about wind flow and snow drifting around avalanche dams, experiments were done in the Jules Verne Climatic Wind Tunnel. The paper reports the results from numerical wind flow simulations that were done to support the findings from the wind tunnel. Satisfying the model similitude criteria for the wind tunnel configuration was difficult due to the inevitable small geometric scale of the model, while on the contrary the snow drifting conditions in the facilities were full scale. By comparing numerical wind flow results of full scale and model scale dams with the snow pattern observed in the wind tunnel, it was possible to conclude that albeit poor model similitude, the snowdrifts on the windward side of the wind tunnel model are likely to indicate the full scale natural situation. 相似文献
110.
P. A. Findlater W. D. Scott S. E. Greenhill J. M. Hopwood 《Environmental Fluid Mechanics》2005,4(4):367-383
A method is developed to estimate the stress at the surface in a portable wind tunnel for wind erosion studies. The boundary layer height and the pressure gradient are used in a simple expression from the Kármán Integral Momentum Equation. Values of friction velocity u
* are within 10% of experimental values obtained through correlation techniques, including measurements of differential pressures with the Murdoch Turbulence Probe MTP and the X-wire, hot-wire anemometer XWA. Wind velocity and stress profiles reveal logarithmic trends and a constant stress layer near the surface in the DAWA portable wind tunnel. Realignment of the statistics with the mean wind is essential. 相似文献