Experimental verification of the gas-hydraulic analogy with reference to the dam-break problem

The results of an experimental study of dam-break waves for both a dry and a flooded bottom in the lower pool are compared with the first approximation of shallow-water theory. It is shown that this approximation adequately describes the height and velocity of the hydraulic jump in the lower pool for a flooded bottom, does not describe the undulations, and is inconsistent with the experimental data on the perturbation propagation velocity in the upper and, for a dry bottom, in the lower pool.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, 2004, pp. 143–152. Original Russian Text Copyright © 2004 by Bukreev, Gusev, A. A. Malysheva, and I. A. Malysheva.     

The Flow Patterns and Wall Stresses in a Louvered‐Wall Moving Granular Filter Bed of Quartz Sand

The flow patterns and wall stresses in a two‐dimensional louvered moving granular filter bed of quartz sand were investigated. The flow pattern histories of granular solids in the filter bed were recorded using a digital camcorder and a pressure gauge for simultaneously measuring the normal stresses as well as shear stresses of the granular solids. The static wall stress distributions produced by the granular solids were measured, and agreed with a theoretical prediction formed using the differential slice and Runge‐Kutta (order four) methods. The variations in the dynamic wall stresses with time in a moving granular filter bed were obtained and the effect of the louver angle upon the flow patterns and wall stresses was also investigated. Employing the results obtained by stress measurements and image processing, the wall pressure pulsation phenomena in a moving granular filter bed may be further understood. The results reported here provide fundamental information for the design of moving granular filter beds to act as high‐temperature flue gas cleanup filters.     

非绝热壁叶栅的粘性流动

非绝热壁叶栅的粘性流动王正明（中国科学院工程热物理研究所北京１０００８０）关键词非绝热壁；叶栅；粘性流动１引言近年来，随着计算机运算速度的提高，叶轮机械内部粘性流动的数值解法发展很快，对于动量方程，已广泛采用亘接求解不作简化的完全的Ｎ－Ｓ方程，以便更...     

Some LC experiments with capillary columns

Some experimental results of LC in capillary columns are presented. The possible effect of turbulence which has been much emphasised lately is overrated. The future of LC in capillary columns lies in extreme miniaturization.     

Local coexistence of different phases

Under intuitively reasonable assumptions it is shown that in two dimensions different phases cannot exist locally. In three dimensions we discuss the possibility of local coexistence of districts with different magnetization for the Heisenberg ferromagnet and show that an interaction that breaks rotational invariance is necessary for this phenomenon.     

Analysis of the magnetic bubble collapse method

In the bubble collapse technique the domain wall mobility is evaluated by measuring the shortest time for which a magnetic bubble collapses. The way in which this evaluation should be carried out is discussed.     

The response of turbulent flow to the disturbance of a vibrating ribbon

By use of the LDV, experimental investigation was carried out for a turbulent boundary layer which was disturbed with an electric-magnetic vibrating ribbon. It is found that, in the flow, the response of the disturbance contains harmonic components besides the fundamental frequency of the ribbon vibration. The fundamental and harmonic disturbances can also enhance the energy of other frequency components around them. In the experiments, the regular disturbane was introduced in the outer region of the boundary layer. Under the given flow conditions, they can significantly influence the downstream coherent structures in the wall region by suppressing the bursts and increasing their period. The effect on the burst period depends on the disturbing frequency. The project supported by the National Natural Science Foundation of China     

强流脉冲电子束作用下纯镍表层中织构及结构缺陷的演化行为

利用强流脉冲电子束(HCPEB)装置对金属纯Ni进行轰击,采用X射线衍射及透射电子显微镜(TEM)技术详细分析了受轰击样品的变形结构和缺陷。X射线衍射分析表明,经强流脉冲电子束处理后,在{111}和{200}晶面出现了择优取向。TEM表层微观结构分析表明:强流脉冲电子束轰击1次和5次后,晶粒内部形成了大量的(111)[112]型波状条带结构,在波状条带内部包含大量平行的(200)[110]型微条带;10次轰击后,样品变形结构发生变化,除大量的条带状结构外,变形孪晶的数量明显增多。这些变形微结构不仅影响表层的织构演化行为,而且还能细化晶粒,强流脉冲电子束技术为制备表面纳米材料提供了一条有效的途径。     

Field-driven creep motion of a composite domain wall in a Pt/Co/Pt/Co/Pt multilayer wire

We have studied the field-driven motion of a pair of coupled Bloch domain walls in a perpendicular magnetic anisotropy Pt/Co/Pt/Co/Pt multilayer Hall bar. The nucleation of an isolated but coincident pair of walls in the two Co layers, observed by Kerr microscopy, took place at an artificial nucleation site created by Ga⁺ ion irradiation. The average velocity v of the wall motion was calculated from time-resolved magnetotransport measurements at fixed driving field H, where the influence of the extraordinary Hall effect leads to the observation of voltages at the longitudinal resistance probes. We observed a good fit to the scaling relation lnv∝H^−1/4, consistent the motion of a single 1-dimensional wall moving in a 2-dimensional disordered medium in the creep regime: the two walls are coupled together into a 1-dimensional composite object.     

Magnetoresistance due to domain wall bulging

The effect of bulging of domain wall (DW) on the magnetoresistance (MR) is investigated. With taking into account the auto-correlation between the points of the interface, one can formulate the mobility within the relaxation time approximation scheme. The results show that the bulging of DW, evaluated with the commonly accepted magnetic parameters for typical ferromagnetic materials of Co, Fe and Ni, has a countable role into the MR.