共查询到19条相似文献,搜索用时 187 毫秒
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对高粘度液体在正弦形波纹壁面上的自由降落和蒸发建立了分析模型。对控制微分方程及边界条件作无量纲处理,引入流函数,采用摄动展开得到了0级近似和一级近似的微分方程组,讨论了液膜的流动和传热特性与壁面之间的关系。 相似文献
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水平螺旋槽管壁面升膜形成机理的研究 总被引:3,自引:1,他引:2
对驱动升膜形成的润湿力进行分析,建立单组分流体的数学模型,得出壁面液膜蒸发时的速度和厚度分布。基于此得到蒸发过程中水平螺旋槽管管外壁升膜的形成机理和流动特性,并给出液膜润湿整个管壁面的临界条件。 相似文献
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采用高速摄像仪对稠密颗粒射流撞击有限尺寸壁面的流动过程进行了实验研究,重点研究了颗粒膜及其表面波纹特征,考察了颗粒粒径、射流速度和固含率等因素对颗粒膜形态和表面波纹的影响.研究结果表明,随着颗粒粒径增大,稠密颗粒撞壁流由颗粒膜向散射模式转变.与液体射流撞壁液膜相比,颗粒膜扩展角较大,射流速度对其影响不显著.稠密颗粒射流撞壁颗粒膜表面波纹存在明显的叠加现象,颗粒膜表面波纹频率比液膜大约低一个数量级.颗粒膜表面波纹主要由射流脉动引起,表面波纹频率与射流脉动频率具有相同的数量级. 相似文献
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一、前言 反环状流和弥散流是临界热流密度后膜态沸腾传热区的二种主要形式。它们分别发生在低含汽率和高含汽率的条件下。反环状流由过冷的液芯和高温壁面处的过热汽膜所组成。主要换热是壁面与蒸汽、蒸汽与液芯表面的换热和壁面与液芯的热辐射。蒸发发生在液芯表面。可视化试验表明,界面有较大的波动,交界面的换热系数很难确定。气膜膜厚变化有两个阶段,初始阶段液芯表面温度尚未达到饱和,无蒸发,因此膜厚不变。经 相似文献
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直喷发动机燃油喷雾撞击壁面形成油膜,导致燃烧效率降低,颗粒物排放增加。伴随撞壁的动态传热过程对油膜蒸发具有重要影响。本文针对正戊烷、甲醇、甲醇汽油混合燃料瞬态喷雾撞击壁面,研究了不同条件下蒸发性对燃油瞬态喷雾撞击壁面动态传热影响。结果表明,提高喷油温度可促进燃油雾化,增大喷油压力或降低喷油距离可提高液滴撞壁强度,缩短液膜存在时间。撞壁瞬态温度与热流密度动态变化特征受燃油蒸发性与喷雾条件联合影响。 相似文献
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本文研究了二维黏性流体薄膜沿非平整不均匀加热基底流动时非线性表面波的演化及其流动稳定性.利用长波摄动法推导出非平整线性加热基底上非线性表面波的零阶和一阶演化方程,基于所得演化方程,绘制出正弦波纹基底上液膜的表面波形图,并研究液膜流动的线性稳定性,分析了各无量纲参数对液膜线性稳定性的影响.分析结果表明:在正弦波纹基底上,液膜自由表面随同壁面作相同频率的正弦型波动,且液膜厚度沿流动方向逐渐变小;Marangoni数为稳定影响因素,随Marangoni数的增大,液膜稳定区域增大;Peclet数和倾角θ均为不稳定影响因素,随Peclet数和倾角θ的增大,液膜稳定区域减小;在非平整基底的波峰和波谷处,Peclet数、Marangoni数和倾角θ对稳定性的影响趋势一致,但基底波谷处的液膜稳定区域小于波峰处区域,流动更易失稳. 相似文献
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针对倾斜随机粗糙壁面上含不溶性活性剂溶液的流动过程, 采用润滑理论建立了液膜厚度和浓度的时空演化模型, 通过PDECOL程序数值求解得到了液膜流/液滴铺展的动力学特性及壁面结构参数的影响. 研究表明: 在重力分量和Marangoni效应共同作用下, 液膜流/液滴铺展速度加快, 液膜边缘和液滴中心出现毛细隆起, 液膜/液滴底部出现凹陷, 同时受粗糙壁面影响, 液膜表面变形更显著. 增加壁面倾角θ具有使重力分量和Marangoni效应增强, 导致隆起和凹陷程度均有所增加的作用. 增大壁面高度D可使液膜流/液滴铺展速度加快, 表面变形放大. 而壁面波数k0则使液膜流/液滴铺展过程减缓, 抑制隆起和凹陷产生. 与液膜流相比, D和k0对液滴铺展速度的影响相对较小.
关键词:
随机粗糙壁面
液膜
Marangoni效应
倾斜流动 相似文献
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Yu. Ya. Trifonov 《Journal of Engineering Thermophysics》2008,17(4):282-291
There are a lot of industrial applications of structured packing. Distillation columns are one of the examples where the liquid
flows over the corrugated surface as a thin film to provide a good mass-transfer surface between the liquid and vapor phase.
The purpose of the present paper is to study the hydrodynamics and the heat-mass transfer of the liquid film spreading down
the corrugated surfaces when the corrugation amplitude is comparable with Nusselt’s film thickness (the amplitude corresponds
to a small texture of the structured packing). As a result, a nonlinear type diffusion equation is obtained to describe the
evolution of the film thickness profile. The nonlinear diffusion coefficient is obtained for three cases: a smooth inclined
plate, a corrugated plate with large ribs, and an inclined corrugated plate with small ribs. The equations are solved numerically.
As a result, it has been obtained that the small texture significantly increases the rate of the film thickness evolution
in comparison with a smooth plate. To obtain the nonlinear diffusion coefficient in the case of a small texture, the hydrodynamics
of the film flow over an inclined corrugated surface are studied. The viscosity, inertia, and surface tension forces are taken
into account. The calculations were carried out on the basis of the Navier-Stokes equations. The influence of the microcorrugations
on both the heat transfer from the wall and the mass transfer through the free surface was investigated. 相似文献
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An approximate method is extended for analyzing the free vibration problem of orthotropic square plate with a square hole. In this paper, a square plate with a square hole is transformed into an equivalent square plate with non-uniform thickness by considering the hole as an extremely thin part of the equivalent plate. Therefore, the dynamic characteristics of a plate with a hole can be obtained by analyzing the equivalent plate. The Green function, which is the discrete solution for the deflection of the equivalent plate, is used to obtain the characteristic equation of the free vibration. The effects of the side to thickness ratio, hole side to plate side ratio and the variation of the thickness on the frequencies are considered. Some numerical analyses are carried out for the simply supported orthotropic square plate with a square hole. The efficiency and accuracy of the numerical solutions by the present method are investigated. 相似文献
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Claus Jönsson 《Zeitschrift für Physik A Hadrons and Nuclei》1961,161(4):454-474
A glass plate covered with an evaporated silver film of about 200 å thickness is irradiated by a line-shaped electron-probe in a vacuum of 10?4 Torr. A hydrocarbon polymerisation film of very low electrical conductivity is formed at places subjected to high electron current density. An electrolytically deposited copper film leaves these places free from copper. When the copper film is stripped a grating with slits free of any material is obtained. 50 Μ long and 0·3 Μ wide slits with a grating constant of 1 Μ are obtained. The maximum number of slits is five. The electron diffraction pattern obtained using these slits in an arrangement analogous to Young's light optical interference experiment in the Fraunhofer plane and Fresnel region shows an effect corresponding to the well-known interference phenomena in light optics. 相似文献
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本文研究一块刚性无约束平板正面击水后激起的水浪和平板在水浪发展过程中的受力过程。将水面边界条件转化为水面高度所该满足的积分微分方程。文中将平板和水面作为一个整体来考虑,通过数值求解得出水对平板作用力随时间的变化以及水面的波浪的发展。 相似文献
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Based upon the spin wave theory, the influence of the size of a three-dimensional Heisenberg system on its thermodynamic properties was studied. It is found that the specific heat increases due to the finite size and free surface of the system. For a magnetic film with finite thickness, the interaction of spin waves was also discussed. There exist three additional scattering processes, namely, the scattering between spin waves with wave-vectors parallel to the surface of the film (two-dimensional spin wave), the scattering between two and three-dimensional waves, and the scattering between those waves with the same component in the direction along the thickness of the film. As a result, the T4 term, arising from the coupling of spin waves, in the expression of the specific heat of the system, splite into three parts proportional to T5/2,T7/2 and T4, respectively. Here T is the temperature. 相似文献