Investigation of flow dynamics of thin viscous films down differently shaped fibers
Investigation of flow dynamics of thin viscous films down differently shaped fibers
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不同形状纤维上粘性薄膜的流动动力学研究
DOI：
10.1063/5.0069189
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发表时间：
2021-11
影响因子：
4
通讯作者：
Chen Xue
中科院分区：
文献类型：
--
作者：
Xie Qirui;Liu Rong;Wang Xun;Chen Xue
纤维上的粘性薄膜的流动动力学与各种工业应用有关。本文通过实验研究了薄膜落在不同形状纤维上的流动行为。对于螺旋光纤，其流动行为表现为三种典型的流型，即孤立流型、瑞利-高原流型和对流流型。然而，各种纤维形状的转变过程是明显不同的。与圆柱形光纤不同，螺旋光纤在瑞利-高原流动状态下的流量范围更大，这有助于在相对稳定的流动状态下精确控制流型。我们进一步定量研究了螺旋纤维流动动力学的三个重要特征参数，即头速度、厚度和间距。结果表明，薄膜在螺旋纤维上具有更高的珠速度、更大的珠厚度和更大的珠间距。我们的发现为理解粘膜在异形纤维上的流动动力学提供了重要的见解，这也可能启发各种应用中的涂层流动控制方法。由AIP出版社独家授权出版。https://doi.org/10.1063/5.0069189沿垂直纤维向下流动的液膜是典型的不稳定流动问题，由于瑞利-高原不稳定性，液膜破裂成液珠或液滴。纤维上的粘性薄膜的丰富动态特性被广泛应用于各种工业应用，如涂层技术、热交换器和蒸汽吸收。在这些应用中，以规则波型控制流动行为的要求很高。例如，以恒定速度和恒定间距控制涂层流动是在光纤上涂覆和光固化周期波形的有效策略。因此，了解沿纤维向下的粘性薄膜的流动动力学是非常重要的。当液体膜沿垂直纤维下落时，重力驱动的流动表现出复杂的界面动力学，包括液滴形成和行波模式。Qu ere首先证明了这种流动行为，他研究了厚膜和薄膜系统中的薄膜破裂特性和液滴形成。Kliakhandler等人观察到三种随流速增加的典型流态：(a)孤立液滴流态，大间距的行珠被小液滴分开；(b)瑞利高原流态，行波以恒定的速度和间隔传播；(c)对流流态，更快更大的下落液滴偶尔发生碰撞。对于行波行为，Duprat等人使用时空图来说明绝对不稳定性和对流不稳定性，其中强调了空间增长。其他实验结果表明，该体系的流动动力学主要受流量、纤维直径和其他流体特性（如粘度和表面张力）的影响。此外，Sadeghpour等人发现喷嘴的几何形状也会改变流动动力学，其中液珠的厚度、间距和速度被用来表征其动力学特性。纤维粘膜涂层是近年来研究的热点。对于薄膜涂层流动，采用基于长波假设的简单模型来研究其线性和非线性动力学。已经证明，由于方位曲率的影响，流动是不稳定的。Liu和Ding提出了一种直接求解Navier-Stokes方程的域映射方法，利用该方法探索了厚液膜的精确定常行波解。近年来，应用物理场对涂层流动的影响得到了广泛的研究。例如，受电场、旋转场和分离压力场影响的热毛细效应流动已被证明是控制涂层流动稳定性和动力学的有效方法。结果表明，施加物理场会使薄膜的绝对不稳定性增强，从而导致薄膜破裂成液滴。达成。理论物理。Lett. 119, 201601 (2021)；doi: 10.1063/5.0069189 119, 201601-1由AIP Publishing Applied Physics Letters ARTICLE scitation.org/journal/apl独家授权出版
The flow dynamics of a thin viscous film down on a fiber is associated with a variety of industrial applications. In this paper, we experimentally investigate the flow behaviors of a thin film falling on differently shaped fibers. For a spiral fiber, flow behaviors show three typical flow regimes as the cylindrical fiber, which indicates the isolated regime, Rayleigh–Plateau regime, and convective regime. However, the transition process of various fiber shapes is distinctively different. Unlike the cylindrical fiber, flow on a spiral fiber exhibits a wider range of flow rate in the Rayleigh–Plateau regime, which is helpful for the precise control of flow patterns in a relatively stable regime. We further quantitatively investigate three important characteristic parameters of flow dynamics of a spiral fiber, i.e., bead velocity, thickness, and spacing. Results reveal that a thin film on a spiral fiber has a higher bead velocity, larger bead thickness, and larger bead spacing. Our findings provide important insights for understanding flow dynamics of a thin viscous film down on shaped fibers, which may also inspire coating flow control methods in various applications. Published under an exclusive license by AIP Publishing. https://doi.org/10.1063/5.0069189 Thin liquid film flowing down vertical fibers is a typical unstable flow problem, and it breaks into liquid beads or drops due to the Rayleigh–Plateau instability. The rich dynamics of a thin viscous film down on a fiber is widely used in various industrial applications such as coating technology, heat exchangers, and vapor absorption. Among these applications, controlling the flow behaviors in a regular wave pattern is highly demanding. For example, controlling the coating flow with constant speed and constant spacing is an effective strategy for coating and photocuring the periodic wave pattern on a fiber. Therefore, it is of great importance to understand the flow dynamics of a thin viscous film down on a fiber. When a liquid film falls down a vertical fiber, the gravity-driven flow exhibits complex interfacial dynamics, including the droplet formation and traveling wave patterns. The flow behavior was first demonstrated by Qu er e, who investigated the film rupture characteristics and drop formation in both thick-film and thin-film systems. Kliakhandler et al. observed three typical flow regimes with increasing flow rates: (a) the isolated droplet regime, where widely spaced traveling beads are separated by small droplets, (b) the Rayleigh–Plateau regime, where a traveling wave propagates with constant speed and spacing, and (c) the convective regime, where faster and larger falling droplets are occasional collision. For the traveling wave behaviors, Duprat et al. used spatiotemporal diagrams to illustrate the absolute and convective instabilities, where the spatial growth is emphasized. Other experimental results show that the flow dynamics in such systems are mainly influenced by the flow rate, fiber diameter, and other fluid properties, e.g., the viscosity and surface tension. In addition, Sadeghpour et al. found that the nozzle geometry also changes the flow dynamics, where the liquid bead thickness, spacing, and velocity are used to characterize its dynamics. The viscous film coating a fiber has been intensively studied in recent years. For a thin film coating flow, simple models based on the long-wave assumption were utilized to investigate the linear and nonlinear dynamics. It has been demonstrated that the flow is unstable due to the azimuthal curvature. Liu and Ding proposed a domain mapping method to solve the Navier–Stokes equations directly, by which the exact steady traveling wave solutions of a thick liquid film are explored. Recently, the effects of applied physical fields on coating flows have been extensively considered. For example, flow with thermocapillary effects, subject to electric fields, rotation fields, and disjoining pressure fields, has proven to be an effective approach to control the stability and dynamics of coating flows. The results showed that applied physical fields may trigger film breakup into droplets due to the enhancement of absolute instability. Appl. Phys. Lett. 119, 201601 (2021); doi: 10.1063/5.0069189 119, 201601-1 Published under an exclusive license by AIP Publishing Applied Physics Letters ARTICLE scitation.org/journal/apl
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影响因子：
3.7
作者：
Liyan Yu;J. Hinch
通讯作者：
Liyan Yu;J. Hinch
沿着旋转纤维流动的液膜的不稳定性和分叉
影响因子：
3.7
作者：
Liu Rong;Ding Zijing
通讯作者：
Ding Zijing
DOI：
10.1016/j.matpr.2021.01.929
发表时间：
2021-03
期刊：
Materials Today: Proceedings
影响因子：
--
作者：
Rahul Sathyanath;Sreeram K. Kalpathy
通讯作者：
Rahul Sathyanath;Sreeram K. Kalpathy
影响因子：
1.8
作者：
D. Quéré
通讯作者：
D. Quéré
影响因子：
9.9
作者：
Sreeram K. Kalpathy;L. Francis;Satish Kumar
通讯作者：
Sreeram K. Kalpathy;L. Francis;Satish Kumar