Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session G15: Jets, Bridges and Rivulets |
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Room: 3022/3024 |
Monday, November 24, 2014 8:00AM - 8:13AM |
G15.00001: Post-breakup solutions of Navier-Stokes and Stokes threads Jens Eggers We consider the breakup of a fluid thread, neglecting the effect of the outside fluid (or air). After breakup, the solution of the fluid equations consists of two threads, receding rapidly from the point of breakup. We show that the bulk of each thread is described by a similarity solution of slender geometry (which we call the thread solution), but which breaks down near the tip. Near the tip of the thread the thread solution can be matched to a solution of Stokes' equation, which consists of a finger of constant spatial radius, rounded at the end. Very close to breakup, the thread solution balances inertia, viscosity, and surface tension (Navier-Stokes case). If however the fluid viscosity is large (as measured by the dimensionless Ohnesorge number), some time after breakup the thread solution consists of a balance of surface tension and viscosity only (Stokes case), and the thread profile can be described analytically. [Preview Abstract] |
Monday, November 24, 2014 8:13AM - 8:26AM |
G15.00002: Dripping dynamics at high Bond numbers Mariano Rubio-Rubio, Paloma Taconet, Alejandro Sevilla When dispensing liquid from a vertically oriented injector under gravity, drops grow at the outlet until the surface tension forces can no longer balance their weight, and the pinch-off occurs. This dripping regime no longer exists above a critical flow rate, at which an abrupt transition to jetting takes place. These phenomena are governed by the liquid properties, the injector size and the injection flow rate, or non-dimensionally, by the Bond, $Bo$, Weber, $We$, and Kapitza, $\Gamma$, numbers. Detailed accounts of the rich dynamics of the dripping regime and the transition leading to jetting can be found in the literature (e.g.\ Phys.\ Rev.\ Lett.\ vol.\ 93, 2004, and Phys.\ Fluids vol.\ 18, 2006), but only for two different values of $Bo$. Therefore, we present new experiments on the dripping dynamics and jetting transition for a wide range of both the liquid viscosity and the size of the injector, reaching values of $Bo$ up to one order-of-magnitude larger than those present in the literature. Our results reveal the existence of new dynamics in the dripping regime not observed at small Bond numbers. In addition, we quantify the hysteresis present in the dripping-jetting transition, previously measured only for the inviscid case. [Preview Abstract] |
Monday, November 24, 2014 8:26AM - 8:39AM |
G15.00003: Pinch-off of threads of nonhomogeneous Polymer solutions Vishrut Garg, Sumeet Thete, Santosh Appathurai, Pradeep Bhat, Osman Basaran Motivated by applications involving inkjet printing of complex fluids, we analyze the nonlinear dynamics of the deformation and breakup of polymeric liquid threads. Virtually all previous such studies have been restricted to situations in which the polymer concentration is uniform within the threads. Recently, Eggers (2014) has proposed that non-uniform polymer concentration can account for the blistering pattern that is sometimes seen during breakup of polymeric threads where at the incipience of pinch-off, the thread has the morphology of small drops that are separated by threads of highly concentrated polymer solution. Following Eggers's approach but one in which he restricted his study to a linear stability analysis, we analyze the full nonlinear dynamics by solving simultaneously Cauchy's momentum equation, the continuity equation, a convection-diffusion equation for the number density of polymers, and a constitutive equation for stress. The latter two equations account for the coupling between polymer concentration and the flow. As the thread profiles seen in experiments are typically quite slender, we expedite the analysis by solving these equations in the slender-jet limit by an approach based on the finite element method. [Preview Abstract] |
Monday, November 24, 2014 8:39AM - 8:52AM |
G15.00004: ABSTRACT WITHDRAWN |
Monday, November 24, 2014 8:52AM - 9:05AM |
G15.00005: Energy-based Classification of Liquid Jet Dynamics: Experiments and Theory Bowen Ling, Ilenia Battiato Experiments and dimensional analysis are used to study the dynamics of Newtonian fluid-air jets. Under quasi-static experimental conditions, new periodic phenomena are first captured by image recognition techniques. The former processes can be described through a newly defined dimensionless modified capillary number. We perform fit-free numerical simulations of appropriately simplified Navier-Stokes equations in different dynamical regimes. Results match the corresponding experimental data and are able to capture important dynamic properties of the system, including dripping-jetting and steady-chaos transitions. [Preview Abstract] |
Monday, November 24, 2014 9:05AM - 9:18AM |
G15.00006: Breakup length of harmonically stimulated capillary jets -- theory and experiments Francisco Javier Garcia Garcia, Heliodoro Gonzalez Garcia, Jose Rafael Castrejon-Pita, Alfonso Arturo Castrejon-Pita A stream of liquid breaks up into several drops by the action of surface tension. Capillary breakup forms the basis of some modern digital technologies, especially inkjet printing (including 3D manufacturing). Therefore, the control and prediction of the breakup length of harmonically modulated capillary jets is of great importance, in particular~in Continuous InkJet systems (CIJ). However, a theoretical model that rigorously takes into account the physical characteristics of the system, and that properly describes this phenomenon did not exist until now. In this work we present a simple transfer function, derived from first principles, that accurately predicts the experimentally obtained breakup lengths of pressure-modulated capillary jets. No fitting parameters are necessary. A detailed description of the theoretical model and experimental setup will be presented. [Preview Abstract] |
Monday, November 24, 2014 9:18AM - 9:31AM |
G15.00007: Laser-induced jet formation in liquid films Frederik Brasz, Craig Arnold The absorption of a focused laser pulse in a liquid film generates a cavitation bubble on which a narrow jet can form. This is the basis of laser-induced forward transfer (LIFT), a versatile printing technique that offers an alternative to inkjet printing. We study the influence of the fluid properties and laser pulse energy on jet formation using numerical simulations and time-resolved imaging. At low energies, surface tension causes the jet to retract without transferring a drop, and at high energies, the bubble breaks up into a splashing spray. We explore the parameter space of Weber number, Ohnesorge number, and ratio of film thickness to maximum bubble radius, revealing regions where uniform drops are transferred. [Preview Abstract] |
Monday, November 24, 2014 9:31AM - 9:44AM |
G15.00008: ABSTRACT WITHDRAWN |
Monday, November 24, 2014 9:44AM - 9:57AM |
G15.00009: Fast liquid transfer between two surfaces Huanchen Chen, Tian Tang, Alidad Amirfazli Liquid transfer process between two surfaces typically ends by breaking of a stretched liquid bridge. The amount of liquid remaining on each of the surfaces relative to total volume is usually of interest in applications (e.g. offset or electronic printing, wet adhesion systems, etc.). Literature shows that depending on stretching velocity, $U$, surface wettability and liquid properties, the behaviour of the liquid bridge can be categorized into: quasi-static where the surface force dominates and dynamic where contributions from viscous and inertia forces are not negligible. Through a systematic experimental study, we demonstrate for the first time that the division of liquid between surfaces in the quasi-static regime is a constant which depends on the receding contact angles. In the dynamic regime (fast transfer), liquid division takes a complicated form. An analytical-empirical model is developed and verified by experimental results that can predict splitting of the liquid between two surfaces as a function of U, surface wettability and liquid viscosity. The model also successfully predicts an even split between surfaces at extremely high velocities as it was observed by us and others. [Preview Abstract] |
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