Capillary-gravity wave scattering from barriers with pinned contact lines

毛细重力波是沿液体自由表面传播的波，通常被限制在狭窄的通道中。这项拟议的研究旨在更好地理解表面波与刚性墙相互作用的基本流体物理。液-气-固三相边界影响液体的行为，这在实验室研究和工业应用中都是重要的，例如，附着在固壁上的液滴的动力学，封闭盆地中的液体振荡，附着在细线圈上的液球和透镜，由螺旋线稳定的液柱，以及开放狭窄通道中的波传播和流动。这项研究提供的理解将有助于开发新的设计和模型，从而实现更有效的液体管理，最大限度地减少固体接触。其结果将适用于工程领域，包括冷凝换热、气液接触过程和化学工程应用，以及在生物和生物技术中的应用。该项目开发的方法还将为测量和模拟涉及三相边界的流体行为提供新的方法。该项目还将有助于STEM劳动力的准备和多样化，包括本科生、研究生和一名职业生涯中期的教职员工。这项拟议的研究将利用实验室和计算实验来提高对传播的毛细重力波从表面相交的刚性屏障散射的基本流体物理的理解，其中接触线将液体的自由表面固定在屏障的边缘。实验室实验将使用一种反射出水面的机载超声波的声学方法来测量毛细重力波的幅度。计算实验将涉及不可压缩和无旋流中的无粘线性波，使用商业软件进行有限元模拟。具体地说，该项目将研究(I)从重力波散射到毛细波散射转变过程中的接触线效应，(Ii)波散射与障碍物几何参数的关系，以及(Iii)液体表面弯曲的障壁处附近的弯月面的影响。在表面张力控制的流体动力学中，了解三相边界处的接触线如何影响自由液体表面的动力学是至关重要的。以往关于接触线对毛细管动力学影响的研究主要集中在驻波模式的频率依赖性和阻尼性。相反，本文的研究将填补具有接触线效应的刚性结构毛细重力波散射的知识空白。自20世纪60年代以来，理论研究一直试图预测接触线对毛细重力波散射的影响，但由于模型中的理想假设的局限性，以及缺乏理解流体物理的实验数据，这一研究进展受到了阻碍。拟议的实验室实验将提供关于接触线对散射的影响的第一个定量结果。实验室和计算实验应该系统地提高散射的流体物理知识，并在接触线和半月板的影响以及对波浪和结构参数的依赖方面产生新的见解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Capillary-gravity waves are waves traveling along free surfaces of liquids and are often confined in a narrow channel. The proposed research is designed with the goal of achieving an improved understanding of the fundamental fluid physics underlying surface wave interactions with a rigid wall. The three-phase liquid-air-solid boundary influences the liquid behavior, which is important in laboratory studies and also in industrial applications, for instance, the dynamics of drops attached to a solid wall, liquid oscillations in closed basins, liquid globes and lenses attached to thin wire loops, liquid cylinders stabilized by helical wires, and wave propagation and flows in open narrow channels. The understanding provided by this research will enable the development of new designs and models that will lead to more efficient liquid management involving minimal solid contact. The results will be applicable to engineering areas including condensation heat transfer, liquid-gas contacting processes, and chemical engineering applications, as well as applications in biology and biotechnology. The approaches developed from this project will also provide new methods for measuring and modeling fluid behavior involving three-phase boundaries. The project will also contribute to the preparation and diversification of the STEM workforce involving undergraduates, graduate students, and a mid-career stage faculty member. The proposed research will use laboratory and computational experiments to improve the understanding of the fundamental fluid physics underlying the scattering of travelling capillary-gravity waves from a surface-intersecting rigid barrier, where contact lines pin the free surface of the liquid at a barrier's edge. The laboratory experiments will use an acoustic method of airborne ultrasound reflected out the water surface to measure the amplitude of capillary-gravity waves. The computational experiments will concern inviscid linear waves in incompressible and irrotational flow by finite-element simulations using commercially available software. Specifically, the project will study (i) contact line effects in the transition from gravity wave scattering to capillary wave scattering, (ii) the dependence of wave scattering on the barrier's geometric parameters, and (iii) the effect of menisci near the barrier walls where the liquid surface is curved. Understanding how contact lines at three-phase boundaries influence the dynamics of a free liquid surface is essential in surface-tension dominated fluid dynamics. Prior studies involving contact line effects on capillary dynamics focused mainly on the frequency dependence and the damping of standing-wave modes. In contrast, the proposed research will fill the gap of knowledge in capillary-gravity wave scattering from rigid structures with contact line effects. Since the 1960s theoretical studies have attempted to predict the contact line effects on capillary-gravity wave scattering, but progress has been hindered by the limitation of ideal assumptions made in the models, and by the lack of experimental data for the understanding of the fluid physics. The proposed laboratory experiments will provide the first quantitative results on the effect of contact lines on the scattering. The laboratory and computational experiments should systematically improve the knowledge on the fluid physics of the scattering and yield new insights on the influence of contact lines and menisci, and on the dependence on wave and structure parameters.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.