扭旋叶片组合方式对静态混合器湍流传热性能的模拟分析

分别对一个截面上安有1～4个扭旋叶片的静态混合器的湍流传热性能进行模拟分析,并利用热量传递势容耗散评价四种组合方式下静态混合器的传热性能.研究结果表明,在相同的粘性耗散条件下,单叶片与双叶片组合的热量传递势容耗散量接近,四叶片组合的热量传递势容耗散量最低,三叶片组合在两者之间;四叶片组合的传热效率最高,三叶片组合次之,双叶片组合与单叶片接近.多叶片组合排列方式形成的多纵向涡明显改善了近壁区二次流速度场与温度场的协同性.     

Plug-In,Clip-On,Tune-Up: A Throwaway Architecture with Optional Extras

For Simon Herron drawing is an innate, even an addictive, compulsion. Here he lets us into his own personal world of drawing: ‘a private haptic language of invention’, which simultaneously has the power to shock and resonate with its time. He traces his graphic lineage back to the work of his father, Ron Herron of Archigram, and projects it forwards through the output of his students.     

The response of reinforced concrete chimneys to vortex shedding

Predicted vortex induced response of circular cross-section reinforced concrete structures is compared with observed full-scale behaviour. On average the predictions agree to within 5% with observations but have a large scatter attributable to the model's failure to recognize the dependence of aerodynamic parameters on free stream turbulence. The high coefficient of variation of the model is, however, not markedly different from that associated with the prediction of drag loads.     

Vortex electromagnetic flow meters for liquid metal coolants

Magnetohydrodynamic (MHD) effects which arise when a magnetic field interacts with a Karman vortex street in the flow of a liquid-metal coolant are considered. The features of MHD effects in light and heavy coolants (for example, sodium and lead) are analyzed. Devices and operating principles of induction and conduction vortex flow-rate converters are described. Data of experiments are presented which enable vortex electromagnetic flow meters to be recommended as an effective means of measuring the flow rate of liquid metals, for example, in nuclear power engineering. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 43–47, January, 2007.     

扇形和圆形气膜冷却直孔的流场和传热实验研究

对锥顶角（扇形角）γ分别为１５°和３０°的垂直扇形气膜冷却单孔射流下游的流场和传热进行了详细的实验研究，并与相同实验条件下圆孔射流的情形进行了比较。结果发现，扇形喷口下游的速度边界层等值线具有两种基本的分布形态，即使在高吹风比Ｍ＝２．０时，扇形孔的下游也没有明显大于主流速度的射流区域出现。吹风比Ｍ≥１．０时喷孔两侧边缘处沿流向形成了一对转向相反、强度较弱的纵向耦合涡。在相同的吹风比下，扇形喷孔出口面积的增大能够有效地降低耦合涡的强度和Ｖ、Ｗ速度分量，从而提高了气膜冷却效率，尤其是提高了喷孔两侧下游位置上的冷却效率。在喷孔中线下游位置上，当吹风比Ｍ＝０．３时，扇形角γ的变化对冷却效率几乎无影响，而当吹风比Ｍ≥１．０时，扇形喷孔较圆孔的冷却效率明显高得多。在喷孔中线两侧ｚ／Ｄ＝１．３的位置上，当扇形角相同时，吹风比低的射流冷却效率较高；当吹风比相同时，扇形角γ＝１５°和３０°的冷却效率非常接近。     

Numerical predictions and stability analysis of cavitating draft tube vortices at high head in a model Francis turbine

Draft tube vortex is one of the main causes of hydraulic instability in hydraulic reaction turbines, in particular Francis turbines. A method of cavitation calculations was proposed to predict the pressure fluctuations induced by draft tube vortices in a model Francis turbine, by solving RANS equations with RNG k-turbulence model and ZGB cavitation model, with modified turbulence viscosity. Three cases with different flow rates at high head were studied. In the study case of part load, two modes of revolutions with the same rotating direction, revolution around the axis of the draft tube cone, and revolution around the core of the vortex rope, can be recognized. The elliptical shaped vortex rope causes anisotropic characteristics of pressure fluctuations around the centerline of the draft tube cone. By analyzing the phase angles of the pressure fluctuations, the role of the vortex rope as an exciter in the oscillating case can be recognized. An analysis of Batchelor instability, i.e. instability in q-vortex like flow structure, has been carried out on the draft tube vortices in these three cases. It can be concluded that the trajectory for study case with part load lies in the region of absolute instability (AI), and it lies in the region of convective instability (CI) for study case with design flow rate. Trajectory for study case with over load lies in the AI region at the inlet of the draft tube, and enters CI region near the end of the elbow.     

一种基于多重涡流新型微混合器的设计与实验

设计了一种基于多重涡流的新型微混合器结构.该结构中多个呈反向分布的规则排列的扩张和收缩结构可产生迪恩流与扩张涡流,基于此,可进行高效率的被动式混合.首先阐述了该结构产生内部迪恩流和扩张涡流的机理,并利用COMSOL软件对该结构进行了液流混合过程的三维数值模拟验证,分析了不同流体流速对多重涡流强弱和混合程度的影响.最后制作了该微混合器,利用2种不同的染料进行了混合实验,通过分析样品的混合效果验证了该混合器的性能.仿真和实验结果均表明:该混合器在低输入流速(0.01 μL/s)和高输入流速(7μL/s)下均可实现高效快速的混合,在0.8cm的距离内即可实现完全混合,在输入流速为5 μL/s时最高混合效率可达98.6％.     

泵站前池流态改善效果的数值模拟分析

针对泵站前池内的流动特点,在分析不同湍流模型,并与试验结果比较的基础上,确定以Realizable k-ε模型作为预测前池漩涡产生与发展及其相应涡量分布的手段,通过大量数值计算,确定了导流墩消涡最佳布置方案,对大型泵站的稳定运行与节能技术改造具有重要借鉴意义.     

Direct numerical simulation of surfactant solution flow in the wide‐rib rectangular grooved channel

The turbulent flow of surfactant solution in the wide‐rib rectangular grooved channels was studied by direct numerical simulation. Moreover, the variations of near‐wall streamwise vortices with time were discussed and the distributions of streamwise vortex radius, swirling strength and density were quantitatively investigated. It was found that the influence of microgrooves on the fluid mainly occurred within the buffer layer and microgrooves could induce numerous streamwise vortices with small size and swirling strength within the grooved valleys. The drag‐reducing enhancement mechanism of microgroove in the surfactant solution could be mainly considered as the competing results between the “restriction effect” and “tip effect” of microgroove, and the essential factor should be the numerous secondary streamwise vortices with small size and swirling strength within the grooved valleys. Furthermore, a predicted method for the optimal drag‐reducing size of microgroove was proposed, and the prediction values agreed well with the numerical results. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2898–2912, 2018     

冲击射流中圆柱尾流的流动特性与分析

本研究通过在冲击射流中设置圆柱棒作可视化观察,分析强化传热机构的流动特性;利用统计分析,探导圆柱棒直径及圆柱间距等对强化传热的影响。