共查询到20条相似文献,搜索用时 93 毫秒
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针对液体在微通道内的自输运特性,采用数值仿真与能量解析相结合的方法研究了液滴在锥形微通道内的自输运特性及力学驱动机制,得到微通道的锥形角、液滴与微通道内壁的接触角及微通道的润湿性对液滴自输运特性的影响关系.分析表明,微通道的锥形角、液滴与微通道内壁的接触角均能影响液滴的自输运方向及驱动力大小.对于亲水性微通道,微通道的锥形角、液滴与微通道内壁的接触角其作用效果呈现整体形态;对于疏水性微通道,微通道的锥形角、液滴与微通道内壁的接触角其作用效果呈现局域形态.这可为研究液体在微通道内的自输运机理及界面内液体细观流动机制奠定理论基础. 相似文献
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研究可压缩液晶方程组强解的破裂准则,建立了一种仅依据于速度梯度的破裂准则,此种准则类似于理想可压缩流情形的Beale-Kato-Majda准则和由Huang和Xin得到的可压缩Navier-Stokes方程组情形的准则.证明用到能量不等式和高阶能量不等式.主要困难是初始密度含有真空. 相似文献
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控制图判断准则的显著性检验 总被引:2,自引:0,他引:2
徐哲,段晓江.控制图判断准则的显著性检验.数理统计与管理,1998,17(3),45~48.利用控制图判断生产过程的状态是一种统计判断,必然犯两种错误。本文在规定“小概率事件”标准的基础上,对休哈特控制图判断准则假设检验的显著性水平进行了分析,并直观解释了各种异常情况的系统性变化特点,最后简述了计算机辅助质量控制图的应用 相似文献
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光测弹性理论中耦联系统的变分原理 总被引:13,自引:0,他引:13
本文提出一能量原理,即光测弹性理论中耦联系统的零差功原理,并据此原理导出了光测弹性理论中耦联系统的势能、余能,广义势能和广义余能变分原理。所谓耦联系统是指形状、尺寸、载荷和边界条件全同且都处于真实状态但材料不同的两个变形体。光测弹性理论中的原型体和模型体实质上是耦联系统,因而上述原理就成为确定柏松比v对冻结应力法精度影响的理论基础。 相似文献
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Lattice Boltzmann Study on the Motion of Dual Droplets in Microchannels With Contact Angle Hysteresis北大核心CSCD 下载免费PDF全文
接触角滞后表现为流体在非理想固体表面上运动时前进接触角和后退接触角不同,是两相流体在润湿表面上流动的重要现象.该文采用改进的伪势格子Boltzmann(LB)多组分模型,并与几何润湿边界条件相结合,研究了两个液滴在具有接触角滞后性微通道表面上的运动行为,主要研究了通道内特征数、通道表面性质以及液滴初始参数的影响.研究结果表明:毛细数的增大有助于液滴的移动,然而并不利于液滴的排出,且毛细数的增加对上游液滴的影响大于其对下游液滴的影响;另一方面,接触角滞后性窗口越大,液滴运动和形变更迟缓,但形变程度更明显,两液滴更早地发生合并,但更晚地排出管道;液滴间距的增加使液滴的运动行为在不同阶段表现为不同的模式,但都导致通道中残留小液滴,使得液滴排出通道的时间增加.研究结果还表明:上游液滴和下游液滴的相对尺寸差距越大,越不利于液滴排出管道. 相似文献
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气流雾化问题中的流动稳定性研究 总被引:6,自引:2,他引:4
运用流动稳定性理论研究气流雾化的机理问题并与有关实验进行比较,证明了界面波失稳引起的不稳定波增长是喷射雾化中液滴形成的主要原因· 另外本文还研究了液滴粒径随各参数的变化规律,理论和实验的结果在一定程度上是符合的,因而它将对喷射成形工艺的研究起到一定的指导作用 相似文献
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A model is developed of aerosol spray for synthesis of sensor film from solution. The synthesis technique considered involves atomization of a solution of mixed salts in methanol, spraying of solution droplets, droplet deposition on a heated substrate, evaporation and chemical reaction to produce mixed oxides, and subsequent film growth. The precise control of oxide nanoparticle size distribution and inter-particle spacing in the film is crucial to achieving high sensitivity. These in turn largely depend on the droplet characteristics prior to impingement on the substrate. This paper focuses on the development of a model to describe the atomization and spray processes prior to the film growth. Specifically, a mathematical model is developed utilizing computational fluid dynamics solution of the equations governing the transport of atomized droplets from the nozzle to the substrate in order to predict droplet characteristics in flight. The predictions include spatial distribution of droplet size and concentration, and the effect on these characteristics of swirling inlet flow at the spray nozzle. 相似文献
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A linear analysis of the Rayleigh–Taylor (R–T) instability on a spherical viscous liquid droplet in a gas stream is presented. Different from the most previous studies in which the external acceleration is usually assumed to be radial, the present study considers a unidirectional acceleration acting on a spherical droplet with arbitrary initial disturbances and therefore can provide insights into the influence of R–T instability on the atomization of spherical droplets. A general recursion relation coupling different spherical modes is derived and two physically prevalent limiting cases are discussed. In the limiting case of inviscid droplet, the critical Bond numbers to excite the instability and the growth rates for a given Bond number are obtained by solving two eigenvalue problems. In the limiting case of large droplet acceleration, different spherical modes are asymptotically decoupled and an explicit dispersion relation is derived. For given Bond number and Ohnesorge numbers, the critical size of stable droplet, the most-unstable mode and its corresponding growth rate are determined theoretically. 相似文献
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研究了平面分层气-液射流在非线性温度分布条件下的界面不稳定性性质.考虑了气体的可压缩性、液体的粘性、以及气体热导率和密度随温度变化等事实.并应用正则模态方法将问题转化为四阶变系数常微分方程,用数值积分和多重打靶法对模型的空间模式进行了计算,研究了不稳定模态随各物理参量的变化趋势.计算表明模型所体现的不稳定性特征与其它模型的计算结果是一致的.同时计算还得出气体和液体的温差越小、雷诺数越大、热导率变大均将有利于液体射流有效雾化的结果.该结论与HJE.Co.Inc(Glens Fails,NY,USA)的实验数据是定性吻合的. 相似文献
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Summary We consider a class of Glauber dynamics for the two-dimensional nearest neighbor ferromagnetic Ising model in which the rate with which each spin flips depends only on the increment in energy caused by its flip in a monotonic non-increasing fashion.We extend to this class results previously shown for the particular case of Metropolis dynamics [NS]. We show that for fixed volume and external field 0<h<1, at very low temperature small rectangular droplets of sping +1 in a sea of spins –1 tend to shrink, while large droplets tend to grow and cover the whole system. The threshold between the two behaviors is sharply defined, the critical length being 2/h.An example is given which shows that without the assumption of monotonicity of the rates this result may be false.We use the result on critical droplets to show that starting from the configuration with all spins down, the systems in the class that we consider evolve in a metastable fashion until the configuration with all spins up is reached.For similar systems in higher dimensions we show that under analogous conditions on the rates, small enough droplets are likely to shrink, while large enough droplets are likely to grow.Partially supported by CNPq. 相似文献
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Flood discharge atomization is a phenomenon of water fog diffusion caused by the discharge of water from a spillway structure, which brings strong wind and heavy rainfall. These unnatural winds and rainfall are harmful for the safe operation of hydropower stations with high water heads. Compared to the method of prototype observations, physical models and mathematical models, which are semi-theoretical and semi-empirical, numerical simulation methods have the advantage of being not limited by a similar scale and are more economical. A finite element model is presented to simulate flood discharge atomization based on water–air two-phase flow in this paper. Equations governing flood discharge atomization are composed of partial differential equations of mass and momentum conservation laws with unknowns for pressure, velocity and the water concentration. The finite element method is used to solve the governing equations by adopting appropriate solution strategies to increase the convergence and numerical stability. Then, the finite element model is applied to a practical project, the Shuibuya hydropower station, which experienced a flood discharge in 2016. Simulation results show that the proposed model can simulate flood discharge atomization with efficient convergence and numerical stability in three dimensions, and good agreement was observed between numerical simulations and prototype observational data. Based on the simulation results, the mechanism of flood discharge atomization was analyzed. 相似文献
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Hans A. Troesch 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1994,45(2):336-344
Zusammenfassung Nachdem insbesondere auch in neueren Forschungsarbeiten immer häufiger Zerstäubungskennlinien durch experimentell fundierte Werte von durchschnittlichen und mittleren Tropfendurchmessern charakterisiert sind, werden in dieser Arbeit solche Werte erstmals mittels der vor cirka 40 Jahren entwickelten Theorie [1, 2] abgeleitet und veröffentlicht. Alle diese spezifischen Durchmesser sind Funktionen der Austauschgrösse 1/ und des maximalen Tropfendurchmessers des Tropfengemisches. Damit werden bisher nicht bekannte Zusammenhänge der verschiedenen spezifischen Durchmesser mittels der Theorie geschaffen. Das Testen der eigenen Theorie an Fremdversuchen verhütet den Vorwurf der Manipulation.
Summary In recent research publications characteristic results of liquid atomization are based on mean and medium diameters of droplets. In the present article such characteristics are discussed on a theoretical base [1, 2]. All these specific diameters are functions of , an exchange parameter in the atomization process, and of the maximum droplet diameter of the droplet-mixture. The result shows, how specific drop diameters can theoretically be brought into dependency upon one another. The testing of this theory with the help of foreign results can prevent the reproach of manipulation.相似文献
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Xiaofeng Ren Juncheng Wei 《Calculus of Variations and Partial Differential Equations》2006,25(3):333-359
A droplet solution characterizes the lamellar phase of a diblock copolymer when the two composing monomers maintain a skewed
ratio. We study the threshold case where the free energy of a droplet solution is comparable to the free energy of the constant
solution. Using a Lyapunov-Schmidt reduction approach, adapted to calculus of variations, we prove the existence of a free
energy local minimizer with a given number of droplets. Also determined are the free energy, the droplet location, and the
droplet size.
Supported in part by a Direct Grant from CUHK and an earmarked Grant of RGC of Hong Kong. 相似文献
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E. A. Carlen M. C. Carvalho R. Esposito J. L. Lebowitz R. Marra 《Journal of Geometric Analysis》2006,16(2):233-264
We prove theorems characterizing the minimizers for the Cahn-Hilliard free energy functional, which is used to describe the
liquid vapor phase transition (or the 2 state magnetization transition). In particular, we exactly determine the critical
density for droplet formation, and the geometry of the droplets. 相似文献