Numerical Analysis of Unsteady Magneto-Biphase Williamson Fluid Flow with Time Dependent Magnetic Field

Numerical investigation of the dusty Williamson fluid with the dependency of time has been done in current disquisition. The flow of multiphase liquid/particle suspension saturating the medium is caused by stretching of porous surface. The influence of magnetic field and heat generation/absorption is observed. It is assumed that particle has a spherical shape and distributed uniformly in fluid matrix. The unsteady two-dimensional problems are modeled for both fluid and particle phase using conservation of mass, momentum and heat transfer. The finalized model generates the non-dimensioned parameters, namely Weissenberg number, unsteadiness parameter, magnetic parameter,heat generation/absorption parameter, Prandtl number, fluid particle interaction parameter, and mass concentration parameters. The numerical solution is obtained. Locality of skin friction and Nusselt number is deliberately focused to help of tables and graphs. While inferencing the current article it is clearly observed that increment of Williamson parameter, unsteadiness parameter, magnetic parameter, volume fraction parameter, and mass concentration parameter reduces the velocity profile of fluid and solid particles as well. And increment of Prandtl number, unsteadiness parameter,volume fraction parameter, and mass concentration parameter reduces the temperature profile of fluid and solid particles as well.     

退火对钛/铜热等静压扩散连接界面的影响

钛/铜(Ti/Cu)作为ITER 第一壁Be/CuCrZr 热等静压连接中间过渡层,形成了多层中间金属相结构,容易在Ti/Cu 金属相之间产生裂纹等缺陷。采用CuCrZr 代替Be,经过与Be/CuCrZr 相同的热等静压工艺,制作了多个CuCrZr/Ti/Cu/CuCrZr 连接件,对Ti/Cu 连接接头进行深入分析。对连接件分别进行未退火、400℃和500℃ 退火处理,去应力退火后对接头强度和缺陷分布的影响进行了研究。研究结果表明,中间钛层的两侧都形成了三层Ti/Cu 扩散层,分别为Cu₄Ti、CuTi 和CuTi₂。纯铜侧的Cu₄Ti 厚度比CuCrZr 侧的厚,使得裂纹几乎全部分布于铜侧的Cu₄Ti 与CuTi 交界处,拉伸样品极易在此处发生脆性断裂。随着退火温度升高,裂纹的产生和扩展减少。     

Dripping retardation with corrugated ceiling

The instabilities of a pendent viscous thin film underneath two corrugated ceilings are studied numerically and theoretically in comparison with the case of a flat wall. With the same initial interface perturbations, it is shown numerically that both the supercritical instability and the subcritical instability can be retarded by the in-phase corrugated ceilings. The lubrication approximation is used to explain the retardation effect of the corrugated ceiling on the supercritical instability of the pendant film, where the linear growth rate is revealed to be power three of the initial film thickness.     

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通过数值模拟及实验研究了润湿性及磁场对液态金属膜流流动状态的影响.首先,通过数值模拟研究了润湿性对膜流流动状态的影响.结果表明,当润湿性不好时,液态金属膜流容易发展为溪状流而不能完全覆盖底壁,入口膜厚较薄时更易发展为溪状流;在入口膜厚及其它情况相同时,密度越小越易发展为溪状流.其次,研究了磁场对膜流流动状态的影响.结果表明,槽道与流体润湿性不好时,有磁场情况下液态金属膜流覆盖底壁的区域较无磁场时增加,强磁场对膜流的湍流有抑制作用.最后,液态金属膜流实验结果表明,润湿性不好时,镓铟锡合金膜流容易收缩发展为溪状流,这与数值模拟的结果是一致的.上述研究结果对磁约束聚变堆液态第一壁的设计具有指导意义.     

Vortex shedding around a near-wall circular cylinder induced by a solitary wave

This study developed a two-dimensional generalized vortex method to analyze the shedding of vortices and the hydrodynamic forces resulting from a solitary wave passing over a submerged circular cylinder placed near a flat seabed. Numerical results for validation are compared with other numerical and experimental results, and satisfactory agreement is found. A series of simulations were performed to study the effects of gap-to-diameter ratio and incident wave height on vorticity pattern as well as the forces exerted on the cylinder. The range of the heights of incident waves is from 0.3h to 0.7h, where h is the still water depth. The range of the gap-to-diameter ratios is from 0.1 to 0.8. The results indicate that the flow pattern and the pressure distribution change significantly because of the close proximity of the seabed where the vorticity flux on the seabed-side surface of the cylinder is suppressed. Placing the cylinder nearer the seabed increases the drag and the positive lift on the cylinder. When the gap-to-diameter ratio increases, the pattern of vortices changes because of the interaction between the main recirculation zone and the shear layers separated from the gap. The maxima of drag, lift and total force increase linearly with the height of the incident wave.     

15×10~4m~3超大型油罐应力测试与数值模拟分析

兰州原油末站大型油罐群,是我国首次在饱和黄土地基修建的大型储油设施。依托其中一座15×104 m3超大型非锚固油罐,开展了现场充水测试罐壁静态应力的试验研究。通过粘贴在油罐罐壁的应变计,测试充水过程中罐壁应力的变化规律,并采用有限元对15×104 m3超大型油罐进行应力分析。测试结果表明:罐壁的环向应力随充水水位的增加基本呈线性关系。数值模拟计算表明,罐壁环向应力最大值发生在第二圈罐壁和第三圈罐壁相连接的位置。由于罐壁上部设置了抗风圈和加强圈,有效地控制了罐壁的径向位移,使罐壁环向应力和竖向轴向应力在加强圈和抗风圈附近发生波动。将有限元数值模拟计算的罐壁环向应力分布情况与实测应力进行比较,两者总体吻合较好。上述研究结果可为超大型储罐在黄土地基的设计和建造提供技术依据和设计参数验证。     

水冷包层模块局部模型流量分配数值模拟

用JAEA 水冷包层(WCSB)模块侧壁的流量分配实验验证了SST 湍流模型,建立了水冷包层模块第一壁的数值分析模型,研究了第一壁各冷却管中的流量分配情况。分析结果发现,第一壁模型入口集管中存在复杂的流动行为,冷却剂可以明显的区分为主流和逆流两大部分,其中主流进入冷却管的位置是影响流量分配的主要因素,逆流区形成了一系列次级涡流和沿管壁的环向流动。分析结果表明,在第一壁模型中,在所以条件下,各冷却剂通道中存在流量分配不均匀现象,流速最大值与最小值偏差均小于2%。     

Spatial relation between fluctuating wall pressure and near-wall streamwise vortices in wall bounded turbulent flow

A new view of the spatial relation between fluctuating wall pressure and near-wall streamwise vortices (NWSV) is proposed for wall bounded turbulent flow by use of the direct numerical simulation (DNS) database. The results show that the wall region with low pressure forms just below the strong NWSV, which is mostly associated with the overhead NWSV. The wall region with high pressure forms downstream of the NWSV, which has a good correspondence with the downwash of the fluids induced by the upstream NWSV. The results provide a significant basis for the detection of NWSV.     

Study on local topology model of low/high streak structures in wall-bounded turbulence by tomographic time-resolved particle image velocimetry

The relationship between the bursting event and the low/high-speed streak in the logarithmic law (log-law) region of a turbulent boundary layer is investigated. A tomographic time-resolved particle image velocimetry (TRPIV) system is used to measure the instantaneous three-dimensional-three-component (3D-3C) velocity field. The momentum thickness based Reynolds number is about 2 460. The topological information in the log-law region is obtained experimentally. It is found that the existence of the quadrupole topological structure implies a three-pair hairpin-like vortex packet, which is in connection with the low/high-speed streak. An idealized 3D topological model is then proposed to characterize the observed hairpin vortex packet and low/high-speed streak.     

实验室隔声测量中试件洞填隙墙传声影响的检验

文章探讨了实验室建筑构件隔声测量中填隙墙传声影响的检验与修正方法。通过实验分析,给出了三种可用于不同隔声量构件的门、窗和玻璃试件隔声测量的填隙墙构造方式。