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Directional migration of single droplet on multi-wetting gradient surface by 3D lattice Boltzmann method
Computers & Fluids ( IF 2.5 ) Pub Date : 2020-02-01 , DOI: 10.1016/j.compfluid.2019.104392
Xin Wang , Bo Xu , Yi Wang , Zhenqian Chen

Abstract Directional migration of single microdroplet on a microstructured surface with multi wetting gradients plays a significant role in many industrial applications. To understand the mechanism of spontaneous movement of microdroplet on wetting gradient surfaces under different gravities, the model of microdroplet dynamics is built by 3D lattice Boltzmann method. Effects of wetting gradient, surface morphology, surface orientation and gravitational force on spontaneous movement are investigated. The results demonstrate that static contact angles are greatly affected by micropillars. Both hydrophilicity and hydrophobicity can be strengthened by micropillar arrays. As a droplet moves from hydrophobic to hydrophilic driven by net capillary force, a transition from partial Cassie state to Wenzel state can be found. A larger wetting gradient and larger solid fraction promote the spontaneous movement of microdroplet. In the process of movement, surface free energy shows an increasing tendency due to part of kinetic energy converted to surface free energy. In spite of two-layer surface capable of maintaining a droplet in partial Cassie state, it will decrease the movement velocity. For Bo ≤ 0.0126, surface orientation has little effect on climbing-upward movement. When the Bo number ranges from 0.0126 to 0.063, gravitational coefficient should be considered in the process of microdroplet (2 μm) climbing- upward movement. The surface with multi wetting gradients can be applied to remove droplets during condensation to enhance heat transfer.

中文翻译:

3D格子Boltzmann方法在多润湿梯度表面上单液滴的定向迁移

摘要 单个微滴在具有多重润湿梯度的微结构表面上的定向迁移在许多工业应用中起着重要作用。为了理解不同重力下微滴在润湿梯度表面上的自发运动机制,采用3D格子Boltzmann方法建立了微滴动力学模型。研究了润湿梯度、表面形态、表面取向和重力对自发运动的影响。结果表明静态接触角受微柱的影响很大。微柱阵列可以增强亲水性和疏水性。当液滴在净毛细管力的驱动下从疏水性移动到亲水性时,可以发现从部分 Cassie 状态到 Wenzel 状态的转变。较大的润湿梯度和较大的固体分数促进微滴的自发运动。在运动过程中,由于部分动能转化为表面自由能,表面自由能呈现增加趋势。尽管两层表面能够将液滴保持在部分 Cassie 状态,但会降低移动速度。当 Bo ≤ 0.0126 时,表面取向对爬升运动的影响很小。当 Bo 数在 0.0126 到 0.063 之间时,微滴(2 μm)爬升运动过程中应考虑重力系数。具有多重润湿梯度的表面可用于在冷凝过程中去除液滴以增强传热。由于部分动能转化为表面自由能,表面自由能显示出增加的趋势。尽管两层表面能够将液滴保持在部分 Cassie 状态,但会降低移动速度。当 Bo ≤ 0.0126 时,表面取向对爬升运动的影响很小。当 Bo 数在 0.0126 到 0.063 之间时,微滴(2 μm)爬升运动过程中应考虑重力系数。具有多重润湿梯度的表面可用于在冷凝过程中去除液滴以增强传热。由于部分动能转化为表面自由能,表面自由能显示出增加的趋势。尽管两层表面能够将液滴保持在部分 Cassie 状态,但会降低移动速度。当 Bo ≤ 0.0126 时,表面取向对爬升运动的影响很小。当 Bo 数在 0.0126 到 0.063 之间时,微滴(2 μm)爬升运动过程中应考虑重力系数。具有多重润湿梯度的表面可用于在冷凝过程中去除液滴以增强传热。表面取向对爬升运动影响不大。当 Bo 数在 0.0126 到 0.063 之间时,微滴(2 μm)爬升运动过程中应考虑重力系数。具有多重润湿梯度的表面可用于在冷凝过程中去除液滴以增强传热。表面取向对爬升运动影响不大。当 Bo 数在 0.0126 到 0.063 之间时,微滴(2 μm)爬升运动过程中应考虑重力系数。具有多重润湿梯度的表面可用于在冷凝过程中去除液滴以增强传热。
更新日期:2020-02-01
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