Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session A13: Drops: Impact on Surfaces IDrops FSI
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Chair: Xiaoyu Tang, Princeton University Room: 506 |
Sunday, November 19, 2017 8:00AM - 8:13AM |
A13.00001: Liquid film on a circular plate formed by a droplet train impingement Toshiyuki Sanada, Shoya Yamamoto Droplet impingement phenomena are found in the wide variety of industrial processes, however the detail of liquid film structure formed by the continuous impact of droplets is not clarified. In this study, we experimentally investigated behavior of liquid film which was formed by a droplet train impact. Especially, we focus on the diameter of hydraulic jump formed on a circular plate. The effects of nozzle diameter, liquid surface tension and liquid flow rate on the jump diameter were investigated. In addition, we compared the liquid film by the droplet train impact with that by a liquid column impact. As a result, the hydraulic jump was observed under the smaller water flow rate condition compare to the liquid column impact. And the jump diameters for the case of droplet train impact were greater than that of liquid column impact. However, the jump diameters for the small surface tension liquid for the case of droplet train impact were smaller than that of liquid column impact. We consider that this phenomenon is related to both high speed lateral flow after droplet impact and splash formation. In addition, the liquid film heights after hydraulic jump on a small circular plate were sensitive to either the droplet train impact or liquid column impact. [Preview Abstract] |
Sunday, November 19, 2017 8:13AM - 8:26AM |
A13.00002: Numerical investigation of drop impact on controlled films using a massively parallelised DNS code: Blue Damir Juric, Idris Adebayo, Lyes Kahouadji, Jalel Chergui, Seungwon Shin, Omar K. Matar We study the outcome of droplet impact on controlled flowing liquid films using a massively-parallelised three-dimensional simulation code – {\it Blue}. The code utilises a domain-decomposition strategy for parallelization with MPI, while the fluid interface solver is based on a parallel implementation of a hybrid front-tracking/level set method. We control the film surface dynamics by an application of periodic inlet-forcing of the film flowrate, which ensures that droplet impact occurs on different, targeted regions of spatio-temporal regularly forming solitary waves, namely flat film, wave humps and capillary waves preceding a large-amplitude wave. The uniqueness and differences between outcomes obtained on these individual regions are then compared qualitatively and quantitatively. Finally, the individual contributions of the film flow rate, droplet speed, and droplet size on the droplet impact outcomes are also studied, and the results validated against previous experimental studies. [Preview Abstract] |
Sunday, November 19, 2017 8:26AM - 8:39AM |
A13.00003: Effect of film control on low inertia drops impacting a flowing film Idris Adebayo, Zhizhao Che, Omar K. Matar Droplet impact is a ubiquitous phenomenon in nature and attracts attraction from any curious observer, due to its aesthetic fascination, and wide-ranging applications. Previous studies in the literature have focused on impact on different types of surfaces (solids and liquids); with the liquid surfaces being either thin, shallow or deep, quiescent or flowing. In this study, we show for the first time, the effect of inlet forcing of the liquid film on the impact outcome for drops with low inertia. We utilise a high-speed camera to visualize the dynamics while customised Matlab routines are developed to analyse the results quantitatively. The effects of important dimensionless quantities such as film Reynolds, drop Weber, and Ohnesorge numbers parameterised by the film flowrate, drop speed, and drop size are also examined. Our results show interesting hither-to undiscovered dynamics brought about by the application of film inlet forcing. [Preview Abstract] |
Sunday, November 19, 2017 8:39AM - 8:52AM |
A13.00004: Numerical simulation of drop impact on interfaces with surfactant effects Jalel Chergui, Assen Batchvarov, Lyes Kahouadji, Damir Juric, Seungwon Shin, Richard V. Craster, Omar K. Matar, Zhizhao Che Direct numerical simulations of droplet impact on a thin film are carried out using {\it Blue}, a front-tracking-based solver. We first vary the droplet size, thickness of the liquid film, and initial droplet height in order to observe the different effects that these parameters have on impact outcomes in the absence of surfactants; this is the `benchmark’ case. The surfactant-laden case is then considered wherein the impact of a drop of surfactant solution on a thin film of the same solution is simulated. The collision outcomes between both clean and surfactant-laden cases are compared. All the results are analysed with the aid of a number of dimensionless quantities such as Bond number, Weber number, and Ohnesorge number. [Preview Abstract] |
Sunday, November 19, 2017 8:52AM - 9:05AM |
A13.00005: Numerical study of viscous dissipation during single drop impact on wetted surfaces Yi An, Shihao Yang, Qingquan Liu The splashing crown by the impact of a drop on a liquid film has been studied extensively since Yarin and Weiss (JFM 1995). The motion of the crown base is believed to be kinematic which results in the equation R$=$(2/3H)$^{\mathrm{1/4}}$(T-T0)$^{\mathrm{1/2}}$. This equation is believed to overestimate the crown size by about 15{\%}. While Trojillo and Lee (PoF 2001) find the influence of the Re not notable. Considering the dissipation in the initial stage of the impact, Gao and Li (PRE, 2015) obtained a well-validated equation. However, how to estimate the dissipation is still worth some detailed discussion. We carried out a series of VOF simulations with special focusing on the influence of viscosity. The simulation is based on the Basilisk code to utilize adaptive mesh refinement. We found that the role of dissipation could be divided into three stages. When T\textless H, relatively small influence of viscosity is expected. When T\textgreater \textgreater 1, the commonly used shallow water equation provides a good approximation while the initial condition should be considered properly. Between this two stages, the viscous dissipation is the governing factor and thus causes inaccurate estimation of the crown base motion in the third stage. [Preview Abstract] |
Sunday, November 19, 2017 9:05AM - 9:18AM |
A13.00006: Impact of droplets on surfaces of immiscible liquid films Zhizhao Che, Omar K. Matar The impact of droplets on surfaces of immiscible liquid films is studied experimentally using high-speed photography. We found that the impact dynamics is significantly affected by the presence of the interface formed between the droplet and the liquid film. The impact of a water droplet on an oil film leads to the formation of a compound crown followed by a central jet. By varying the impact speed of the droplet, different impact outcomes are analysed, including bouncing, deposition, and oscillation of the impact droplet, the formation and the collapse of the compound crown, and the formation and tip-pinching of the central jet. The effects of key parameters controlling the impact process are discussed, such as the Weber number and the Ohnesorge number of the droplet, the viscosity ratio between the two immiscible fluids, and the film thickness. [Preview Abstract] |
Sunday, November 19, 2017 9:18AM - 9:31AM |
A13.00007: Measurement of the penetration of a falling droplet in wet granular medium Zhehan Zhong, William Steinhardt, Shima Parsa, Elad Stolovicki, Jiankun Zhuo, David Weitz, Qiang Yao We measure the penetration depth and pattern of the impact of a droplet on a pre-wetted granular pack of PMMA particles in 3D using high speed imaging and a scanning laser sheet. The index of refraction of the wetting fluid and the falling droplet are matched the particles so imaging in 3D is made possible. Using a high speed camera and scanning laser sheet, we are able to directly visualize the impact of the droplet, the speed and direction of the penetration and also the distribution of granular material. We have systematically varied the speed of the impact by changing the height of the droplet and find that the impact affect a limited depth of the packing of the granular material. [Preview Abstract] |
Sunday, November 19, 2017 9:31AM - 9:44AM |
A13.00008: Axisymmetric study of drop interface impact in viscous flow Xiaoming Zheng, John Lowengrub This work studies the effects of Reynolds number and Weber number on the rebounding phenomena in the drop/interface impact problem in a viscous flow. A drop falls through a viscous liquid and then impacts a liquid interface at the bottom. The drop may break to a ring in the falling process. In the impact, the drop may rebound or coalesce on contact. In this numerical study, we assume the drop falling and impacting processes are axisymmetric. We use axisymmetric finite element level-set method and adaptive mesh to solve the Navier-Stokes equations to simulate this process. After extensive parameter studies, we find that there is a range of Weber numbers dependent on the Reynolds numbers, within which the drop rebounds, below which the drop would coalesce directly with interface, and above which the drop may break into a ring. [Preview Abstract] |
Sunday, November 19, 2017 9:44AM - 9:57AM |
A13.00009: Effect of the pool depth on drop impact splashing Hossain Chizari, Marie-Jean Thoraval We investigate the effect of the pool depth on the splashing dynamics of drop impact. The splashing of a single drop impacting into a deep pool or on wet surface has been investigated for many years both numerically and experimentally. However, recent results have demonstrated the importance of the vorticity produced during the impact on the splashing behavior. More specifically, the shedding of a vortex ring inside the liquid during the impact can separate the splash jet into several parts. The shedding of the vorticity can be influenced by the proximity of the bottom of the pool, if the pool depth is small enough. We study here how the pool depth can affect the vorticity shedding and the resulting splashing jets. We perform axisymmetric numerical simulations of the impacts with the open sources codes Gerris and Basilisk, and systematically vary the impact conditions, focusing on the effect of pool depth in the splashing regimes. [Preview Abstract] |
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