多热源分布时薄层液体中热毛细对流的分叉特征

本文研究一个液体薄层在热源作用下的流动特征。Pimputakar和Ostrach给出了单热源作用下薄层液体的高度和流场方程。本文在此基础上具体分析比较了多个热源分布作用下的流动图象随各参数尤其是随热源间距离不同的变化情况，着重讨论产生的分叉现象。     

什么是龙卷风

龙卷风大多发生在高温、高湿的不稳定气团中。那里空气剧烈地抖动,导致上下温度相差过大,冷空气急剧下降,热空气迅速上升,上下层空气快速对流,在空中形成小旋涡,近地面几十米厚的一薄层空气     

Emission characteristics and combustion instabilities in an oxy-fuel swirl-stabilized combustor

This paper presents an experimental study on the emission characteristics and combustion instabilities of oxy-fuel combustions in a swirl-stabilized combustor. Different oxygen concentrations （Xoxy=25%-45%, where Xoxy is oxygen concentration by volume）, equivalence ratios （φ=0.75-1.15） and combustion powers （CP= 1.08-2.02 kW） were investigated in the oxy-fuel （CH4/CO2/O2） combustions, and reference cases （Xoxy=25%-35%, CH4/N2/O2 flames） were covered. The results show that the oxygen concentration in the oxidant stream significantly affects the combustion delay in the oxy-fuel flames, and the equivalence ratio has a slight effect, whereas the combustion power shows no impact. The temperature levels of the oxy-fuel flames inside the combustion chamber are much higher （up to 38.7%） than those of the reference cases. Carbon monoxide was vastly produced when Xoxy〉35% or （φ〉0.95 in the oxy-fuel flames, while no nitric oxide was found in the exhaust gases because no N2 participates in the combustion process. The combustion instability of the oxy-fuel combustion is very different from those of the reference cases with similar oxygen content. Oxy-fuel combustions excite strong oscillations in all cases studied Xoxy=25%-45%. However, no pressure fluctuations were detected in the reference cases when Xoxy〉28.6% accomplished by heavily sooting flames which were not found in the oxy-fuel combustions. Spectrum analysis shows that the frequency of dynamic pressure oscillations exhibits randomness in the range of 50-250 Hz, therefore resulting in a very small resultant amplitude. Temporal oscillations are very strong with amplitudes larger than 200 Pa, even short time fast Fourier transform （FFT） analysis （0.08 s） shows that the pressure amplitude can be larger than 40 Pa.     

油田注水井流量计现场应用效果分析

本文分析了油田套损区注水井流量计目前状况，介绍了四种流量计的工作原理，并通过对34口注水井流量计的应用情况进行跟踪对比，论述了高压干式水表出现负偏差的原因、机械传动与电子技术结合后的优缺点，旋涡流量计的应用状况，提出了旋涡流量计完全代替高压干式水表设想，对避免因仪表误差影响油田注水、提高注水质量有一定的指导作用。     

“魔鬼海岸”探秘

挪威的森林大名鼎鼎,其实那不过是徒有虚名——仅仅因为作曲家格里格的一首乐曲被日本作家村上春树演绎成一个书名罢了。挪威的魔鬼海岸才是世界上独具魅力的景观。其魅力在于峡湾里潋滟的波光下暗藏着无尽玄机、佛罗埃岛和罗弗敦岛之间惊天动地的大旋涡以及至今还在流传着的北欧海盗洗劫整个欧洲的故事。     

金星上的"怪异旋涡"

金星是地球在太阳系的行星邻居之一,由于它的大气层十分浓厚,因此,天文学家对金星的了解很少。不过,金星的两极有十分巨大的大气旋涡,人们很早以前就发现了这种明显的大气结构。     

柱状结构条纹列板对尾涡形态变化的影响机理

为研究柱状结构条纹列板对尾涡形态变化的影响机理,用粒子图像测速(Particle Image Ve-locimetry,PIV)系统对绕有螺旋条纹列板的圆柱尾流进行测量,分析和探讨不同列板条纹高度对柱状结构尾涡形态变化的影响.通过计算流体力学(Computational Fluid Dynamics,CFD)数值计算,模拟条纹列板对圆柱尾流的扰动.结果显示,螺旋条纹列板显著影响边界层、剪切层的形成及尾流旋涡脱落形态,破坏柱状结构尾流正负旋涡交替,从而起到抑制尾流周期性旋涡脱落的作用.     

科学疑难：流水与浓烟

在自然界中,流水总是打着旋儿向前,浓烟总是旋转着飘散,大气也容易形成旋涡状气流,这些普通常见的景观竟然蕴藏着深刻的科学难题,令科学家至今头痛难解。     

浅谈大型热水锅炉振动事故的原因及处理措施

文章对几起热水锅炉振动事故的原因做了分析,阐述了对锅炉振动事故的处理方法。     

浅析北美多温带气旋的原因

温带气旋是指存在于中纬度地区的水平空气旋涡，是中纬度地区重要的天气系统。从分布看，温带气旋在北美发育最多，对北美天气、气候的影响也最以为强烈。