Simulation of Free-Surface Flow in a Tank Using the Navier-Stokes Model and Unstructured Finite Volume Method

Modelling free-surface flow has very important applications in many engineering areas such as oil transportation and offshore structures. Current research focuses on the modelling of free surface flow in a tank by solving the Navier-Stokes equation. An unstructured finite volume method is used to discretize the governing equations. The free surface is tracked by dynamically adapting the mesh and making it always surface conforming. A mesh-smoothing scheme based on the spring analogy is also implemented to ensure mesh quality throughout the computaiton. Studies are performed on the sloshing response of a liquid in an elastic container subjected to various excitation frequencies. Further investigations are also carried out on the critical frequency that leads to large deformation of the tank walls. Another numerical simulation involves the free-surface flow past as submerged obstacle placed in the tank to show the flow separation and vortices. All these cases demonstrate the capability of this numerical method in modelling complicated practical problems.

发泡镍对肺冲击伤的防护效果及其机理研究

本研究采用激波管,探讨了发泡镍对肺冲击伤的防护效果和防护机理。结果表明,发泡镍可明显减轻肺冲击伤的程度,降低死亡率。发泡镍的防护作用可能与其降低冲击波超压峰值、延长正压上升时间和缩短正压作用时间有关。结果提示发泡镍是一种较为理想的冲击伤防护材料。

损伤材料裂纹尖端附近的应力场

本文导出了损伤材料的全量理论,导出了全量公式中H的渐近表达式;最后得到损伤材料平面应变条件下的裂纹尖端的应力应变场。

自持电激励横流CO_2激光器的最佳输出功率

本文研究了横流CO_2激光器电激励区的形状、光腔位置、反射镜的大小、耦合度、介质流速诸因素对输出功率的影响,得到了一批规律性的结果,可为实验研究和器件设计提供参考。

中小型锅炉的化学清洗与节能

<正> 一、前言 我国中小型锅炉(从工作压力来分类,一般是低压锅炉,即p<20kg/cm~2)数量庞大,全国约20万台,耗煤量大,每年耗煤近2亿吨.它们的运行效率很低,造成能源的巨大浪费,其重要原因之一,是锅炉的受热面上,常沉积着导热系数很低的水垢,它导致锅炉传热效率的下降,从而使锅炉热效率下降,煤耗量增大.根据我国有关单位对六省三市九万台

地震孕育发展的力学过程和地震预报

<正> 地震的孕育发展,主要是和地壳的受力、变形、能量的逐步积累和集中、岩层突然断裂和错动、应变能释放、发生地震及震后的调整等有关的力学过程,同时伴随着地球物理、地球化学的变化,并且是与大气物理、天体物理等有联系的复杂过程。 地震力的产生,与地球自转速率的变化、地球内部物质的流动与能量的转化等因素有关,是一个复杂的尚未完全弄清的问题。

化学输运动力学过程的数学模型

本文从化学流体力学观点出发,对应用相当广泛的一类化学输运动力学过程进行了理论分析,建立了数学模型,求得了数学解.在此基础上,提出了化学输运动力学过程的等价单元系及生产作业序列的记忆效应等有实际意义的概念.

A model of an isolated magnetic-flux tube in a stratified atmosphere

A two-dimensional model of a magnetic flux tube confined in a gravitational stratified atmosphere is discussed. The magnetic field in the flux tube is assumed to be force-free. By using the approximation of large scale height, the problem of a free boundary with nonlinear conditions may be reduced to one involving a fixed boundary. The two-dimensional features are obtained by applying the perturbation method and adopting the Luest-Schlueter model as the basic state. The results show that the configuration of a flux tube confined in a gravitational stratified atmosphere is divergent, and the more twisted the magnetic field, the more divergent is the flux tube.

Generation of 17-TW 23-fs pulses with a two-stage Ti : Sapphire amplifier at repetition rate 10 Hz

We have developed a two-stage Ti:sapphire amplifier system which can produce 17-TW/23-fs pulses at a repetition rate 10 MHz. A birefringent plate is used in the regenerative amplifier to alleviate gain narrowing, while an all-reflective cylindrical-mirror-based pulse stretcher and an acousto-optic programmable dispersive filter (AOPDF) are used to compensate for the higher order dispersion of the system.

Improvement of sensitivity and refractive-index changes in LiNbO3 : Ce : Cu crystals with UV light

A nonvolatile recording scheme is proposed using LiNbO3:Ce:Cu crystals and modulated UV light to record gratings simultaneously in two centres and using red light to bleach the grating in the shallow centre to realize persistent photorefractive holographic storage. Compared with the normal UV-sensitized nonvolatile holographic system, the amplitude of refractive-index changes is greatly increased and the recording sensitivity is significantly enhanced by recording with UV light in the LiNbO3:Ce:Cu crystals. Based on jointly solving the two-centre material equations and the coupled-wave equations, temporal evolutions of the photorefractive grating and the diffraction effciency are effectively described and numerically analysed. Roles of doping levels and recording-beam intensity are discussed in detail. Theoretical results confirm and predict experimental results.

Spectroscopic, and thermal studies of some new binuclear transition metal(II) complexes with hydrazone ligands containing acetoacetanilide and isoxazole

A new chelating ligand, 2-(2-(5-tert-butylisoxazol-3-yl)hydrazono)-N-(2,4-dimethylphenyl)-3-oxobutanamide (HL), and its four binuclear transition metal complexes, M-2(L)(2) (mu-OCH3)(2) [M = Ni(II), Co(II), Cu(II), Zn(II)], were synthesized using the procedure of diazotization, coupling and metallization. Their structures were postulated based on elemental analysis, H-1 NMR, MALDI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films of these complexes on K9 glass substrates were prepared using the spin-coating method and their absorption properties were evaluated. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC. Different thermodynamic and kinetic parameters namely activation energy (E

Comparison of ZnO films grown on before- and after-vapor transport equilibration (VTE) LiAlO2 substrates by pulsed laser deposition (PLD)

About Phi 45 mm LiAlO2 single crystal was grown by Czochralski (Cz) technique. However, the full-width at half-maximum (FWHM) value was high to 116.9 arcsec. After three vapor transport equilibration (VTE) processes, we can obtain high-quality LiAlO2 slice with the FWHM value of 44.2 arcsec. ZnO films were fabricated on as-grown slices and after-VTE ones by pulsed laser deposition (PLD). It was found that ZnO films on the two slices have similar crystallinity, optical transmittance and optical band gap at room temperature. These results not only show that LAO substrate is suitable for ZnO growth, but also prove that the crystal quality of LAO substrate slightly affects the structural and optical properties of ZnO film.