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 引用本文: 李国辉, 吴小雨, 王娴. Oldroyd-B黏弹性液滴撞击弯曲壁面的数值研究. 力学学报, 2024, 56(4): 1-14.
Li Guohui, Wu Xiaoyu, Wang Xian. Numerical simulation of Oldroyd-B viscoelastic droplets impacting a curved wall. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(4): 1-14.
 Citation: Li Guohui, Wu Xiaoyu, Wang Xian. Numerical simulation of Oldroyd-B viscoelastic droplets impacting a curved wall. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(4): 1-14.

## NUMERICAL SIMULATION OF OLDROYD-B VISCOELASTIC DROPLETS IMPACTING A CURVED WALL

• 摘要: 液滴撞击弯曲壁面现象广泛存在于冶金、化工和航空航天等领域, 在某些场景下, 液滴混入高分子聚合物后会表现黏弹性特性, 为了进一步认识液滴黏弹性对撞击弯曲壁面的影响, 对黏弹性液滴撞击弯曲壁面的过程进行数值模拟研究. 研究基于相场方法和格子玻尔兹曼(LBM)方法, 采用应力场分布函数求解Oldroyd-B本构方程, 并施加适用于弯曲壁面的接触角模型, 发展了固−液−气三相黏弹性流体模拟方法, 对Oldroyd-B黏弹性液滴撞击弯曲壁面问题进行数值模拟, 主要研究了黏度比 \beta 、韦伯数We和壁面接触角 \theta 对撞击过程的影响. 结果表明: 撞击过程主要包括4个阶段: 运动阶段、铺展阶段、拉伸阶段和撕裂阶段. 黏度比 \beta 越低, 液滴在铺展拉伸阶段动能衰减越慢, 转化的表面能更多, 但更早进入撕裂阶段, 液滴撞击弯曲壁面后, 更容易脱离壁面. 韦伯数We较小时, 液滴主要在壁面处附着或反弹; We较大时, 液滴会撕裂并脱离壁面, We越大, 液滴在铺展拉伸阶段动能衰减越快, 进入撕裂阶段更慢. 壁面的亲疏水性会影响液滴最终的状态, 疏水性越高, 对铺展阶段的阻碍作用越强, 液滴越容易发生撕裂和脱离.

Abstract: The phenomenon of droplets impact on a curved wall widely exists in fields such as metallurgy, chemical engineering, and aerospace. In certain scenarios, droplets mixed with polymers may exhibit viscoelastic properties. Therefore, in order to further understand the influence of droplet viscoelasticity on the impact of curved walls, numerical simulation research was conducted on the process of viscoelastic droplets impacting curved walls. Based on the phase field method and lattice Boltzmann method (LBM), a three-phase viscoelastic flow field simulation method was developed to numerically simulate the impact of an Oldroyd-B viscoelastic droplet on a curved wall, in which the stress field distribution function solves the Oldroyd-B constitutive equation, and the contact Angle model of the curved wall is applied. The main focus is on the influence of viscosity ratio, Weber number, and wall contact angle on the impact process. The results indicated that the impact process consists of four main stages: the motion stage, the expansion stage, the stretching stage, and the tearing stage. As viscosity ratio β decreases, the kinetic energy decays faster in the expansion and stretching stage, the converted surface energy increases, and it enters the tearing stage earlier. After the droplet impacts the curved wall, it is easier to detach from the wall. The droplet mainly adheres or rebounds on the wall surface when the Weber number is small, and may tear and detach from the wall when the Weber number is large. As the Weber number increases, the kinetic energy of the droplet decays more rapidly during the expansion and stretching stage, and it enters the tearing stage more slowly. The hydrophilicity and hydrophobicity of the wall surface affect the final state of the droplet. The higher the hydrophobicity, the stronger the obstruction effect on the spreading stage, and the easier it is for the droplet to tear and detach.

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