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91.
In this paper, three liquids flowing in five pipes with the same inner diameter of 14 mm were studied to determine the relationship between the surface wettability and flow properties in laminar flow(Re b 2000). This was motivated by oilfield observations of increased pressure drops in non-metallic pipes compared to those in metal pipes,which was contrary to expectations. A new expression for the frictional coefficient that considers the Reynolds number and contact angle θ in laminar flow for non-metallic pipes was proposed based on the experimental results of single-phase flow using dimension and regression analyses. The solutions of the anomalous phenomenon were proposed from the perspectives of the pipe diameter, contact-angle difference, and the compatibility between flexible composite pipe and JLHW105 oil according to the new formula. The surprising finding was that the surface wettability could control the frictional resistance by the critical contact angle(39.9°) obtained at the same Reynolds number. If 0° b θ≤ 39.9°, the frictional coefficient increased as the contact angle increased. In contrast, if 39.9° b θ b 180°,the frictional coefficient decreased with increasing contact angle. The influences of the pipe diameter and contactangle difference on the pressure drop difference of JLHW105 oil showed an inversely proportional relation. A series of materials and liquids were tested. The selection of pipe material for transporting a given fluid can be based on the contact angle, surface tension, and critical limit of the contact angle obtained. The research results are expected to provide some guidelines for the selection of the appropriate pipe material for a given set of fluids. 相似文献
92.
93.
目的研究Q235碳钢在静止和流动条件下腐蚀程度和主要腐蚀区域的差异。方法使用丝束电极(WBE)技术和电化学阻抗谱(EIS)技术分别研究了WBE在静止和流动条件下的电流密度分布、电荷转移电阻以及腐蚀形貌的变化和差异,同时分析了电极的极性转换现象。结果流动条件下Q235碳钢的电荷转移电阻明显降低。在静止条件下,Q235碳钢表面阳极电流区域所占的最大比例为47%,且阳极电流峰集中出现在WBE的中间区域,而四周边缘处的阳极电流峰较少。在流动条件下,Q235碳钢表面的阳极电流区域所占的最大比例为58%,阳极电流峰随机分布在整个WBE表面,且电流分布区间明显变窄。浸泡在静止条件下的58~#电极和流动条件下的39~#电极发生了多次极性转换现象。结论 Q235碳钢在静止和流动条件下均发生了明显的不均匀腐蚀现象。流动条件加剧了Q235碳钢的腐蚀且降低了腐蚀不均匀性。静止条件下Q235碳钢的腐蚀区域集中在中间区域,流动条件下Q235碳钢的腐蚀区域随机分布在整个碳钢表面。静止和流动条件下的钢电极均发生了电流的极性转换现象。 相似文献
94.
《中国有色金属学会会刊》2020,30(3):678-687
The effects of microstructure inhomogeneity on the mechanical properties of different zones in TA15 electron beam welded joints were investigated using a micromechanics-based finite element method. Considering the indentation size effect, the mechanical properties for constituent phases of the base metal (BM) and heat affected zone (HAZ) were determined by the instrumented nano-indentation test. The macroscopic mechanical properties of BM and HAZ obtained from the tensile test agree well with the numerical results. The incompatible deformation between the constituent phases tends to localize along the softer primary phase α where failure usually initiates in form of localized plastic strain. Compared with the BM, the mechanical properties of constituent phases in the HAZ differ substantially, leading to more serious strain localization behavior. 相似文献
95.
96.
97.
A three-dimensional heat flux model for deep-penetrating electron beam welding (EBW) is established to mathematically describe the physical heat generation process during interaction between electrons and the dynamic molten pool free surface. Monte Carlo method is used to determine the electron-target interaction, and random distribution of initial electrons, progressive trajectory tracing and electron backscattering models are used to describe the spatial distribution of electrons absorption. The model is verified in preset keyholes and applied in the simulation on electron beam welding process, and the calculated bead shape shows a good consistency with experimental results. 相似文献
98.
独居老人如在室内或室外发生意外摔倒时,没有得到及时医疗救助治疗,将给老年人造成巨大的心理与身体的伤害。
将航姿参考系统(attitude and heading reference system,AHRS)应用在跌倒检测中,将跌倒的过程转变成姿态的变化,从而来判断
跌倒的程度。 AHRS 航姿系统比过去原有实验方案 3 种姿态角度均有所提升,俯仰角( pitch)提升 2. 371%,滚转角( roll)提升
9. 238%,偏航角(yaw)提升 4. 682%,加速度计最大值精确了 0. 171g,AHRS 航姿系统融合扩展卡尔曼滤波器在检测老年人跌倒
姿态中比过去原有实验方案在检测时间计算上提升了 1 s。 综上实验验证 AHRS 航姿融合在检测老年人跌倒上可以数据更精
确,计算时间更少,在研究人体真实跌倒姿态中更贴近了一步。 相似文献
99.
《International Journal of Hydrogen Energy》2019,44(31):16898-16908
Dynamic contact angle (DCA) plays a critical role in the numerical investigation of gas-liquid two-phase flow problem in proton exchange membrane fuel cells (PEMFCs). In our previous study, an advancing-receding DCA (AR-DCA) model was developed based on Hoffman function and has been successfully validated. This study aims to further modify the contact line velocity evaluation method in the AR-DCA model and an improved-AR-DCA (i-AR-DCA) model is proposed. The simulations of droplet impact on inclined surface and liquid water behaviors in microchannel are conducted based on these two models and the results show that the improved methodology has no significant effects on general droplet spreading process on inclined surface; whereas it can facilitate the liquid water detachment in the microchannel. In addition, the Hoffman function is modified into three different forms based on the original experimental data points in order to test the sensitivity of different formulae on the numerical results. It is indicated that the modified forms of Hoffman function can induce notable changes in the liquid water slug elongation in the microchannel. 相似文献
100.
《International Journal of Hydrogen Energy》2022,47(31):14339-14345
The ZnTe material has an unprecedented role in the fabrication of high efficiency CdTe thin film solar cells and optimization of hydrogen annealing induced physical properties of ZnTe films is next required step. Consequently, in the present work, the impact of Hydrogen annealing temperature on the structural, optical, electrical, topographical, morphological, and compositional properties of ZnTe films is explored. The ZnTe thin films (having 300 nm thickness) are grown via electron-beam evaporation technique on glass and ITO substrates followed by annealing at different temperatures under a Hydrogen atmosphere. The ZnTe films are found to crystallize in cubic phase with (111) predominant peak having crystallite size in the range of 19–28 nm, whereas annealed films demonstrated lower optical transmittance vis-à-vis to pristine films. The PL spectra exhibit two luminescence peaks with a stronger band at ~351 nm and a weaker band at ~450 nm. Ohmic behavior of ZnTe films is assured through I–V characteristics, while the AFM images revealed hill-like surface topographies. The FESEM image of pristine films demonstrated a homogeneous surface comprising spherical grains whereas annealed films have spherical, stone, and blisters like morphologies. The EDS patterns assured the Te element richness as well as successful ZnTe films deposition. The observed findings signify that the Hydrogen annealing at different temperatures notably modified the physical properties of ZnTe films. 相似文献