L形和U形三维钝体结构绕流的数值模拟研究

采用大涡模型对L形和U形三维钝体建筑物的绕流特性和风压分布特性进行数值研究.考虑平均和脉动速度入口边界,在雷诺数为1.5×105～7×105条件下,对2种钝体的9种分析工况进行瞬态动力分析,并将计算结果与已有研究进行对比.研究表明,钝体绕流对周围流场影响的强弱程度依次为尾流区、屋顶区、来流区,影响大小随着流场与钝体之间...     

低溶解氧对苦草生长的影响

针对太湖梅梁湾生态净化示范区内重建的沉水植物存在的腐烂死亡问题及伴随的底层水体溶解氧偏低现象,在室外模拟生态系统内进行了低氧对沉水植物（苦草）生长的影响试验。结果表明：无论沉积物类型如何,一个月的低氧处理（溶解氧平均值为1.6 mg/L）对苦草株重、株高、分蘖数及叶片数等指标的影响均不明显,对块茎的影响则较显著,表现为块茎数量与重量显著下降。对岸边沉积物处理组而言,低氧对苦草根系的影响显著,表现为根须变细且数量增加,根系活力明显下降,中心沉积物处理组则不显著。同时,低氧处理使岸边沉积物处理组的沉积物氧化还原电位显著下降、水体营养盐浓度上升,尤其是磷酸盐浓度显著增加,中心沉积物处理组的环境理化因子变幅则相对较小。分析认为,低氧对苦草生长的影响虽不明显,但对其种群扩张有潜在的不利作用;梅梁湾生态净化示范区内沉水植物的腐烂死亡,低氧的作用是次要或间接的。     

热阻力概念的修正及计算方法

以隧道火灾为背景,对一维加热管流中的热阻力进行了研究。通过压力场数值模拟与理论分析,直接证实了热阻力的存在,并表明传统概念上的热阻力明显大于实际的能量损失。根据能量方程提出水平无粘管流的热阻力应等于气流经过加热区的全压力降,而非静压力降;等截面管流的热阻力大小应为传统热阻力值的1/2。这一修正使热阻力概念具有了严格的流体力学意义。在定义新的热阻力系数基础上,建立了2个热阻力系数表达式及低马赫数条件下热阻力的近似表达式。将该近似表达式与热损失方程进行对比,表明两者在低马赫数条件下具有一致性。研究成果进一步发展了热阻力理论体系,对隧道火灾及其它相关工程热物理问题的研究与应用都具有重要价值。     

Toluene removal characteristics by a superimposed wire-plate dielectric barrier discharge plasma reactor

A superimposed wire-plate dielectric barrier discharge reactor was used to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene decomposition were investigated. It was found that an optimal toluene removal was achieved when the oxygen content was about 5%. Under this condition, the highest toluene removal efficiency of 80.8% was achieved when the gas concentration was 80 mg/m^3. The toluene removal efficiency decreased with the increase of the gas flow rate and the initial concentration of toluene. In addition, the ozone concentration decreased with the increase of the initial concentration of toluene. It suggested that combining DBD （dielectric barrier discharge） with Co3O4/Al2O3/foam nickel catalyst in-situ could improve the toluene removal efficiency and suppress ozone formation. Products analysis showed that the main products were CO and CO2 when oxygen was more than 5%.     

呼吸效应对矿井封闭火区氧浓度的影响分析

为避免因火区封闭导致重大安全事故发生,通过采集某矿井1 d内3个不同监测点的大气压力变化情况,建立大气压力波动模型并分析计算,同时建立火区内外压差100,750 Pa情形下的氧浓度模型进而获得火区内侧氧气浓度因呼吸效应,在不同压差、体积大小火区、风阻、瓦斯涌出量、封闭时刻等多因素耦合影响下随时间的变化规律,以评估火区危险性。研究结果表明:井下大气随地面大气周期波动,封闭火区内、外侧之间的气压差因外界大气波动呈现16 h的余弦波动和8 h的线性波动周期变化;密闭质量好的火区具有更好地抗干扰性,内侧氧浓度的降低主要依靠瓦斯稀释;密闭质量差的火区,内侧氧浓度易受到火区涌出瓦斯、外界涌入大气双重影响;火区氧浓度在2%~12%之间波动,以至火区存在发生瓦斯爆炸的可能性;火区内外压差较大时,氧浓度波动变化幅度更大,危险作用持续时间更长。结合火区氧浓度波动模型,可有效地对矿井火区采取安全的防范措施,避免瓦斯爆炸事故发生。     

变压器油池火燃烧规律的实验研究*

为对变压器油池火灾进行准确有效的灭火,研究不同尺寸和不同厚度下变压器油的火灾动力学特征和基本燃烧特性,具体分析变压器油的燃烧过程和变压器油燃烧速率、火焰温度以及辐射热流随油池直径以及厚度的变化规律。结果表明:整个油品的燃烧过程分为预热燃烧阶段、稳定燃烧阶段和火焰熄灭阶段。对于厚度大于10 mm的油池燃烧,稳定阶段的燃烧速率与油层厚度无关,稳定阶段的燃烧速率随着油池直径的增加而增加。同时,变压器油火灾连续火焰区温度接近750 ℃。对于稳定燃烧阶段下的变压器油燃烧,基于辐射通量可得出在燃烧过程中,辐射热量占总燃烧热的占比约为1/3。研究结果可丰富变压器油燃烧的基础数据,为变压器火灾的灭火提供参考。     

隧道救援站通风网络优化设计及人员疏散研究*

为确定铁路隧道救援站最佳通风结构,对烟道布置提出合理建议,采用计算流体力学（CFD）的方法,对铁路隧道救援站通风网络进行优化设计。同时,采用模拟计算的方法对救援站人员疏散进行模拟分析,确定救援横通道布置及防护门开度设置的合理性。研究结果表明:在同等通风参数工况设置下,采用多节点排烟竖井结构后各救援横通道流量分配更均匀,救援站压力平衡性更好,通风效率可提升15%;通过疏散模拟证实,在长560 m的紧急救援站范围内设置10条疏散横通道,横通道设1.7 m宽的逃生门能够满足疏散要求。     

突发事件下安全舆情的传播与演变——以江苏响水天嘉宜化工有限公司“3.21”特别重大爆炸事故为例

为明确突发事件安全舆情传播与演变路径,提高企业防控突发事件安全舆情传播风险能力,降低衍生灾害发生概率,在文献分析及事故致因理论基础上,构建突发事件安全舆情传播与演变过程的系统动力学（SD）模型,并运用Vensim软件对以江苏响水天嘉宜化工有限公司“3.21”特别重大爆炸事故为例进行仿真实验,模拟安全舆情传播与演变动态过程。结果表明:突发事件安全舆情传播与演变主要受事件自身、媒体、相关企业监管层、相关企业执行层4个主体的共同影响,其中事件自身因素起效时间最早,相关企业监管层影响作用最大、维持时间最持久,相关企业执行层影响最直接。     

Time perspective balance and team adaptation in dynamic task contexts

The concept of time perspective balance has attracted increased attention from scholars in the past decade, reflected in published evidence suggesting positive outcomes ranging from enhanced mood to life satisfaction for those individuals possessing balance among their past, present, and future time perspectives, and assumedly able to shift their time perspective to match situational demands. In this paper, we consider the notion of time perspective balance in an organizational setting within which much consequential adaptation often occurs—the team environment—and explore different configurations of time perspective balance in teams facing dynamic task contexts. Drawing from work on situational awareness, we first consider the mechanism by which time perspective balance likely influences individual adaptation in dynamic task-focused situations. Next, we postulate what types of team configurations—ones with more balanced time perspective uniformity or ones with more time perspective variety—might be more appropriate in dynamic contexts given key team conditions. We illustrate our analysis with examples from healthcare team settings and offer ideas for future research.     

Recent application of Computational Fluid Dynamics (CFD) in process safety and loss prevention: A review

In recent years, significant progress has been made to ensure that process industries are among the safest workplaces in the world. However, with the increasing complexity of existing technologies and new problems brought about by emerging technologies, a strong need still exists to study the fundamentals of process safety and predict possible scenarios. This is attained by conducting the corresponding consequence modeling and risk assessments. As a result of the continuous advancement of Computational Fluid Dynamics (CFD) tools and exponentially increased computation capabilities along with better understandings of the underlying physics, CFD simulations have been applied widely in the areas of process safety and loss prevention to gain new insights, improve existing models, and assess new hazardous scenarios. In this review, 126 papers from 2010 to 2020 have been included in order to systematically categorize and summarize recent applications of CFD for fires, explosions, dispersions of flammable and toxic materials from accidental releases, incident investigations and reconstructions, and other areas of process safety. The advantages of CFD modeling are discussed and the future of CFD applications in this research area is outlined.