共查询到20条相似文献,搜索用时 31 毫秒
1.
Luís O. E. dos Santos Fabiano G. Wolf Paulo C. Philippi 《Journal of statistical physics》2005,121(1-2):197-207
The dynamics of capillary flow has several practical applications in the industry and has been extensively investigated. The
main focuses in these studies are the motion of the interface, especially near the three-phase contact line, and the change
of contact angle during the invasion process. In this work we present several simulations results of capillary invasion in
two- and three-dimensions, using the Lattice–Boltzmann model based on field mediators. We investigate the velocity field near
the solid surface, the changes in the contact angle as a consequence of the flow, and the boundary conditions that can be
used in the inlet and outlet of the capillary tube. In all simulations the diameter of tube is made large enough to enable
the evaluation of the contact angle directly from the density field and the results of capillary rise are compared with a
theoretical model based on the Bosanquet equation, which includes capillary, viscous, inertial and gravitational effects. 相似文献
2.
3.
S. Chibbaro L. Biferale F. Diotallevi S. Succi 《The European physical journal. Special topics》2009,171(1):223-228
We present a systematic study of capillary filling for a binary fluid by using mesoscopic a lattice Boltzmann model describing
a diffusive interface moving at a given contact angle with respect to the walls. We compare the numerical results at changing
the ratio the typical size of the capillary, H, and the wettability of walls. Numerical results yield quantitative agreement with the theoretical Washburn law, provided
that the channel height is sufficiently larger than the interface width and variations of the dynamic contact angle with the
capillary number are taken into account. 相似文献
4.
利用落塔的短时微重力条件, 实验研究了与容器连通的毛细管中的流体在微重力条件下的毛细流动过程, 并通过理论分析建立了相应的毛细管中弯月液面高度随时间变化的微分方程. 结果表明, 对于不同的接触角和不同的容器/毛细管参数, 由建立的理论公式得到的数值解结果都与实验结果在定量上较为一致. 此外, 实验中发现, 改变乙醇和去离子水混合液的比例可以明显地改变接触角参数, 但对毛细流动的影响很小, 建立的理论公式也对这一现象给出了合理的解释. 该研究对于预测和分析微流道及空间微重力条件下的毛细流动行为具有明显的应用价值. 相似文献
5.
基于润滑理论,采用滑移边界条件建立了二维液滴厚度的演化模型和移动接触线动力学模型,利用数值计算方法模拟了均匀加热基底上固着液滴蒸发时的动力学特性,分析了液-气、固-气和液-固界面张力温度敏感性对壁面润湿性和液滴动态特性的影响.结果表明,液滴的运动过程受毛细力、重力、热毛细力和蒸发的影响,重力对液滴铺展起促进作用,而毛细力、热毛细力则起抑制作用;通过改变界面张力温度敏感性系数,可使液滴蒸发过程中的接触线呈现处于钉扎或部分钉扎模式,且接触线钉扎模式下的液滴存续时间低于部分钉扎模式;提高液-气与液-固界面张力温度敏感系数均可改善壁面润湿性能,加快液滴铺展速率;而增大固-气界面张力温度敏感系数则导致壁面润湿性能恶化、延缓液滴铺展过程;通过改变固-气界面张力温度敏感系数更有利于调控处于蒸发状态下的液滴运动. 相似文献
6.
A. Lévy T. Ceccotti H. Popescu F. Réau P. D’Oliveira P. Monot Ph. Martin J. P. Geindre E. Lefebvre 《The European physical journal. Special topics》2009,166(1):111-116
We present a systematic study of capillary filling for
multi-phase flows by using mesoscopic lattice Boltzmann models describing a diffusive
interface moving at a given contact angle with
respect to the walls. We compare the numerical results at changing
the density ratio between liquid and gas phases, δρ/ρ
and the ratio, δξ/H, between the typical size of
the capillary, H, and the interface width, δξ.
It is shown that numerical results yield quantitative agreement with the
Washburn law when both ratios are large, i.e. as the
hydrodynamic limit of a infinitely thin interface is approached.
We also show that in the initial stage of the filling process, transient behaviour
induced by inertial effects and “vena contracta” mechanisms, may induce
significant departure from the Washburn law.
Both effects are under control in our lattice Boltzmann
equation and in good agreement with the phenomenology of capillary filling. 相似文献
7.
Long-range electrostatic fields deform the surface profile of a conductive liquid in the vicinity of the contact line. We have investigated the equilibrium profiles by balancing electrostatic and capillary forces locally at the liquid vapor interface. Numerical results show that the contact angle at the contact line approaches Young's angle. Simultaneously, the local curvature displays a weak algebraic divergence. Furthermore, we present an asymptotic analytical model, which confirms these results and elucidates the scaling behavior of the profile close to the contact line. 相似文献
8.
通过用毛细管测量纯水表面张力系数实验,得到管内径d与接触角θ的相对误差之间的关系曲线,由此说明实验测得的表面张力系数α和理论公式相比呈现一定的偏差,并简单地讨论了实验的理想状态与实际情况的差别. 相似文献
9.
S. Chibbaro 《The European physical journal. E, Soft matter》2008,27(1):99-106
We present a systematic study of capillary filling for a binary fluid by using a mesoscopic lattice Boltzmann model for immiscible
fluids describing a diffusive interface moving at a given contact angle with respect to the walls. The phenomenological way
to impose a given contact angle is analysed. Particular attention is given to the case of complete wetting, that is contact
angle equal to zero. Numerical results yield quantitative agreement with the theoretical Washburn’s law, provided that the
correct ratio of the dynamic viscosities between the two fluids is used. Finally, the presence of precursor films is experienced
and it is shown that these films advance in time with a square-root law but with a different prefactor with respect to the
bulk interface. 相似文献
10.
11.
Vibrated sessile drops: Transition between pinned and mobile contact line oscillations 总被引:1,自引:0,他引:1
Noblin X Buguin A Brochard-Wyart F 《The European physical journal. E, Soft matter》2004,14(4):395-404
We study the effects of vertical vibrations on non-wetting large water sessile drops flattened by gravity. The solid substrate is characterized by a finite contact angle hysteresis (10-15 degrees). By varying the frequency and the amplitude of the vertical displacement, we observe two types of oscillations. At low amplitude, the contact line remains pinned and the drop presents eigen modes at different resonance frequencies. At higher amplitude, the contact line moves: it remains circular but its radius oscillates at the excitation frequency. The transition between these two regimes arises when the variations of contact angle exceed the contact angle hysteresis. We interpret different features of these oscillations, such as the decrease of the resonance frequencies at larger vibration amplitudes. The hysteresis acts as solid friction on the contour oscillations, and gives rise to a stick-slip regime at intermediate amplitude.Received: 4 April 2004, Published online: 10 August 2004PACS:
47.55.Dz Drops and bubbles - 68.08.Bc Wetting - 47.35. + i Hydrodynamic waves 相似文献
12.
采用分子动力学模拟方法研究单壁碳纳米管在石墨基底上的运动.首先碳纳米管在基底弛豫至平衡状态,然后对其施加一固定外力,撤去外力后,碳纳米管在基底上逐渐减速至停止.为了研究管径、手性角对运动方式的影响,本文选择了C(10,10),C(10,9),C(10,8),C(10,5),C(10,0),C(8,8)六种单壁碳纳米管进行模拟.结果表明,碳纳米管在石墨基底上的运动方式由手性角决定,与管径无关.手性角等于30°时,碳纳米管与石墨基底之间为公度结构,碳纳米管的运动出现周期性的滑动和翻滚现象;手性角大于28.3°小于30°时,碳纳米管一边向前滑动一边滚动;手性角小于26.3°时,碳纳米管在基底上滑动.碳纳米管的手性角决定了它与石墨基底接触界面的微观构型,从而决定了碳纳米管的运动方式.
关键词:
分子动力学模拟
碳纳米管
动能
结构公度性 相似文献
13.
K.G. Winkels I.R. Peters F. Evangelista M. Riepen A. Daerr L. Limat J.H. Snoeijer 《The European physical journal. Special topics》2011,192(1):195-205
Instabilities of receding contact lines often occur through the formation of a corner with a very sharp tip. These dewetting
structures also appear in the technology of Immersion Lithography, where water is put between the lens and the silicon wafer
to increase the optical resolution. In this paper we aim to compare corners appearing in Immersion Lithography to those at
the tail of gravity driven-drops sliding down an incline. We use high speed recordings to measure the dynamic contact angle
and the sharpness of the corner, for varying contact line velocity. It is found that these quantities behave very similarly
for Immersion Lithography and drops on an incline. In addition, the results agree well with predictions by a lubrication model
for cornered contact lines, hinting at a generic structure of dewetting corners. 相似文献
14.
We study the origins of the dynamic contact angle in a two-dimensional lattice-Boltzmann model of immiscible fluids. We show that the dynamic contact angle changes as a function of capillary number as observed in laboratory experiments and explain how this dependence arises in the lattice-Boltzmann model. We also explain how the fluid-fluid interface can move while retaining its shape. The interface has an apparent slip length. The apparent slip follows the classical Navier slipping rule where the velocity of the fluid at the wall is proportional to the viscous stress at the wall. This apparent slip length is proportional to the viscous length scale associated with the spurious flow induced by uncompensated stress at the three-phase contact point. 相似文献
15.
Sara Zahedi Katarina Gustavsson Gunilla Kreiss 《Journal of computational physics》2009,228(17):6361-6375
A new model for simulating contact line dynamics is proposed. We apply the idea of driving contact-line movement by enforcing the equilibrium contact angle at the boundary, to the conservative level set method for incompressible two-phase flow [E. Olsson, G. Kreiss, A conservative level set method for two phase flow, J. Comput. Phys. 210 (2005) 225–246]. A modified reinitialization procedure provides a diffusive mechanism for contact-line movement, and results in a smooth transition of the interface near the contact line without explicit reconstruction of the interface. We are able to capture contact-line movement without loosing the conservation. Numerical simulations of capillary dominated flows in two space dimensions demonstrate that the model is able to capture contact line dynamics qualitatively correct. 相似文献
16.
文章从静力和动力学的角度简要回顾了关于沿内角的自发毛细流动研究的最近进展.作为一个通用几何形状,内角在地面微观尺度下或处于失重状态的航天飞行器系统内大尺度下为液体提供有效的输运通道.当一定的几何条件得到满足并且当毛细力远远大于体力比如重力的时候,沿着内角会发生自发毛细力驱动流动现象.从静力学的角度来说,本文讨论的自发毛细驱动流动和当特定的边界条件发生突然变化,比如重力作用突然消失时带有内角的容器内部单值有限高度的平衡自由面的非存在性有关系. Concus-Finn方法可以用来确定这样的平衡自由面在一个横截面处处一致的柱形容器内的非存在性.用这个方法可以推导出在失重状态下一个内角为2α的通常柱形容器里,当接触角小于π/2-α时,平衡曲面不存在.通常来说,沿内角的自发毛细驱动流动属于层流.利用尺度分析和摄动法,成功分析了该流动的动力学特性,并且推导出对设计有用的封闭形式的解析解.一个典型的结果是在黏性流的范畴里毛细面端点的移动和t1/2成正比 相似文献
17.
Simulation and Experiments on the Capillary Force between a Circular Disk and a Parallel Substrate 下载免费PDF全文
《中国物理快报》2017,(5)
The capillary force of a liquid bridge with a pinned contact line between a small disk and a parallel plate is investigated by simulation and experiments. The numerical minimization simulation method is utilized to calculate the capillary force. The results show excellent agreement with the Young-Laplace equation method. An experimental setup is built to measure the capillary force. The experimental results indicate that the simulation results agree well with the measured forces at large separation distances, while some deviation may occur due to the transition from the advancing contact angle to the receding one at small distances. It is also found that the measured rupture distance is slightly larger than the simulation value due to the effect of the viscous interaction inside the liquid bridge. 相似文献
18.
The surface free energy, or surface tension, of a liquid interface gives rise to a pressure jump when the interface is curved. Here we show that a similar capillary pressure arises at the interface of soft solids. We present experimental evidence that immersion of a thin elastomeric wire into a liquid induces a substantial elastic compression due to the solid capillary pressure at the bottom. We quantitatively determine the effective surface tension from the elastic displacement field and find a value comparable to the liquid-vapor surface tension. Most importantly, these results also reveal the way the liquid pulls on the solid close to the contact line: the capillary force is not oriented along the liquid-air interface, nor perpendicularly to the solid surface, as previously hypothesized, but towards the interior of the liquid. 相似文献
19.
We discuss the behaviour of 4He meniscus on various disordered Cs substrates. We have first studied the dynamics of the contact line on Cs substrates evaporated at low temperature. The activated motion of the line is consistent with a substrate disorder of mesoscopic length scale. We have performed further studies of the contact line behaviour on substrates with roughness of macroscopic length scale. Close to the wetting transition, we find that a film invades the substrate leading to marked changes in the value of the contact angle. 相似文献
20.
To probe the microscopic balance of forces close to a moving contact line, the boundary conditions around viscous drops sliding down an inclined plane are investigated. At first, the variation of the contact angle as a function of the scale of analysis is discussed. The dynamic contact angle is measured at a scale of 6 mum all around sliding drops for different volumes and speeds. We show that it depends only on the capillary number based on the local liquid velocity, measured by particle tracking. This velocity turns out to be normal to the contact line everywhere. It indirectly proves that, in comparison with the divergence involved in the normal direction, the viscous stress is not balanced by intermolecular forces in the direction tangential to the contact line, so that any motion in this last direction gets damped. 相似文献