Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session L09: Drops: Complex Fluids |
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Chair: Fei Duan, Nanyang Technological University Room: Ballroom I |
Monday, November 25, 2024 8:00AM - 8:13AM |
L09.00001: Illustrating flow patterns for hydrothermal waves in sessile droplets Fei Duan The sessile droplet phase change, occurring in many engineering applications, has been reported with showing the complex temperature patterns. The hydrothermal waves (HTWs) are one of the observed phenomena; however, they are not well explained through experiments. We thus designed the tests to illustrate the sessile droplet lifetime though the infrared (IR) camera and particle image velocimetry (PIV) measurements. The droplets were maintained with the constant contact radius in the most lifetime on the heated substrate during the measurement. The agreements are found between the IR images and the micro-PIV measurements for linking HTWs to the convective cells for the sessile droplets. The convective cells are generated by the capillary flow and thermocapillary flow with the interfacial complex temperature gradients near the droplet contact line. The contact angles are critical for forming of the HTWs. Three stages of the evolution of the instability in the phase-change droplets are identified. The splitting and merging of the HTW patterns in the IR measurement can be explained with the flow field from the micro-PIV as well. |
Monday, November 25, 2024 8:13AM - 8:26AM |
L09.00002: Numerical and theoretical analysis for deformation of a ferrofluid droplet in shear flow under magnetic field Yuto Kawabata, Shunichi Ishida, Yohsuke Imai We numerically investigated a deformation of a ferrofluid droplet in shear flow under the uniform magnetic field. We employed the boundary integral method to calculate the incompressible two-phase Stokes flow and the magnetic field governed by Maxwell’s equation. In the validation problems, we checked that the simulation results were in good agreements with previous numerical and theoretical studies. Our simulation results suggested that imposing magnetic fields perpendicular to the shear flow suppresses the droplet deformation and breakup. |
Monday, November 25, 2024 8:26AM - 8:39AM |
L09.00003: Composite drop formation in immiscible liquid during interfacial solute transfer Muzammilanwar S Khan, Amol A Kulkarni We observe formation of multicomponent drop in multiphase environment in nature, science and technology. An obvious phenomena for an ordinary person, and classic problem for researchers due to its rich dynamics and implications in broad range of applications. Here, we experimentally study composite drop formation at fixed, submerged position inside stagnant liquid (continuous) phase, where interfacial transfer of one of the drop components occurs simultaneously into continuous phase. We report novel transition in drop formation regime from axisymmetric drop – deformed drop – deformed, oscillating drop – dripping, with a change in composition of drop phase. Results were confirmed by conducting multiple side, top-view experiments. Shadowgraphy was used to visualize solute diffusion, helping us to better understand its implications on drop formation time and volume. We quantitatively measure real time variations in drop size by in-house developed image analysis method. We show that solute extraction can be intensified by controlling drop formation time in such systems away from equilibrium. |
Monday, November 25, 2024 8:39AM - 8:52AM |
L09.00004: An Experimental Investigation on Colloidal Droplet Behavors in a Freezing-Based Inkjet Three-dimensional (3D) Printing Method Haipeng Zhang, Xiaoxiao Zhang, Yang Liu Inkjet-based three-dimensional (3D) printing is an additive manufacturing technology that has received much attention in recent decades. In this method, liquid droplets of ink are dripped onto a substrate. After drying, the liquid phase evaporates, but solid particles of printing materials in the ink remain and form the desired structure on the substrate. During a typical evaporation-based drying process, fluidic motions into droplets affect the distribution of solid particles. Thus, the resolution and uniformity of printed patterns are limited. In this study, we developed a novel freezing sublimation-based method to improve printing quality: the printed inkjet droplets were frozen onto the substrate. Afterward, a sublimation-based drying process removed liquids from the frozen pattern. Using this method, a rapid freezing process of inkjet droplets improves the adhesivity of printing materials on different surfaces, widening the applicable working conditions of the inkjet-based 3D printing method. In addition, a sublimation-based drying process shifts the frozen liquid phase into a gaseous phase, which minimizes the internal flow of the liquid phase during the drying process. Thus, this method significantly improved the uniformity of materials in a printed structure. In this study, we experimentally proved the concept of this proposed method and investigated the effects of printing conditions on the quality of printed patterns. |
Monday, November 25, 2024 8:52AM - 9:05AM |
L09.00005: Abstract Withdrawn
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Monday, November 25, 2024 9:05AM - 9:18AM |
L09.00006: High-fidelity simulations of viscoelastic filament dynamics undergoing airflow-induced thinning and breakup Thomas Abadie, Konstantinos Zinelis, Gareth H McKinley, Omar K Matar, Jesse Capacelatro Flow resulting from a cough or sneeze is inherently multi-phase and multi-scale, as it involves the dispersion of small liquid droplets in a gaseous fluid. Understanding the multi-phase nature of expiratory flow and its potential to suspend small droplets for longer durations than would have otherwise occurred in single-phase jets can be crucial for accurate predictions of respiratory disease infections. To this end, it is also critical to develop sophisticated models capable of capturing the non-Newtonian flow behavior in these settings. Here, we consider axisymmetric simulations of impulsively started viscoelastic jets, identifying the effects of the injection flowrate, the fluid elasticity, and the extensibility of the polymer chains on the rate-of-thinning and the pinch-off singularities. In addition, we perform three-dimensional simulations of viscoelastic jets, using Adaptive Mesh Refinement (AMR) to investigate the role of non-axisymmetric perturbations in the jet profile. Specifically, we study numerically the thinning and breakup process of a viscoelastic ligament induced by a transverse airflow. In this configuration, we simulate a viscoelastic filament of saliva attached to human lips undergoing deformation due to air flow generated by the corresponding vocalization. We examine the role of viscoelastic effects in controlling morphology and the dynamic response to the imposed deformation compared to the Newtonian case. Sub-grid scale modelling strategies to accelerate the computations, which make use of high-fidelity simulation data, are also discussed. |
Monday, November 25, 2024 9:18AM - 9:31AM |
L09.00007: Transparent self-heating plasmonic metasurfaces using ink-jet printing technology Hyoungsoo Kim, Byeong Eun Jeon, Jeongsu Pyeon, Dong Jae Kim, Sung-Wook Yoon Recently, we developed photothermal plasmonic metasurfaces consisting of cellulose nanocrystals (CNCs) and anisotropic gold nanorods (GNRs). To fabricate these metasurfaces, we prepared co-assembled CNC-GNR particles that created a well-aligned annular ring pattern after complete evaporation. The CNC-GNR films were self-heated by plasmonic effects under visible wavelengths. The temperature increase of the film varied depending on the concentration of GNRs in the coated pattern. To achieve a high temperature increase, the concentration of GNRs needed to be high, making the film non-transparent. To expand its application areas, we used ink-jet printing to fabricate a transparent self-heating plasmonic metasurface. We experimentally investigated the optimal conditions for ink-jet printing to achieve high-resolution printing fidelity. This work not only charts a new physicochemical pathway for next-generation nanomaterials based on CNC control but also highlights the potential of these materials to advance the field of nanotechnology. We believe that this could benefit applications in aircraft and vehicle de-icing systems and photonic device thermal management. |
Monday, November 25, 2024 9:31AM - 9:44AM |
L09.00008: Size-dependent colloidal deposits of impacting droplets on an incline: role of impact speed and inclination angle Bibek Kumar, Sanghamitro Chatterjee, Rajneesh Bhardwaj
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Monday, November 25, 2024 9:44AM - 9:57AM |
L09.00009: Influence of Ferrofluid Drop Shapes on Cavity Formation During Impact on a Liquid Pool Moaz Kattoah, Ziqiang Yang, Sigurdur T Thoroddsen Ferrofluids are liquids that become strongly magnetized in the presence of a magnetic field, and they have applications in various fields including medical devices, electronics, and mechanical components. This experimental study examines how magnetic fields can change the shapes of impacting ferrofluid drops. The drops were made to fall into a pool of water, influenced by an electromagnet positioned beneath the tank. By adjusting the electromagnet's pulse duration through an external trigger box, the drops were shaped into either prolate or oblate forms before impact. The electromagnet was deactivated just before the drops hit the water, preserving their shapes while halting magnetic effects. As oil-based ferrofluids do not mix with water, the shape of the drop affected the formation and evolution of the resulting cavities. We measure the maximum depth and diameter of these irregular-shaped cavities in relation to impact velocity and drop shape. Findings indicated that drops with prolate shapes created deeper cavities compared to spherical and oblate drops. |
Monday, November 25, 2024 9:57AM - 10:10AM |
L09.00010: Drop shape’s influence on the maximum impact radius and maximum impact force Yang Zeng, Zhen Chen, Lei Xu Using ferrofluid, we realize various drop shapes and illustrate its fundamental role in drop impact on a solid surface. We study the influence of drop’s aspect ratio and discover that both the maximum spreading radius and the maximum impact force systematically depend on the aspect ratio. We explain the maximum radius with the viscous dissipation model and the maximum force with the high-stress cylinder model, which agree with the experiment nicely. |
Monday, November 25, 2024 10:10AM - 10:23AM |
L09.00011: Dynamic self-assembly of microparticles in rotating drops under acoustic levitation Ranjiangshang Ran, Justin C Burton Atmospheric aerosol such pollen, volcanic ash, and dessert dust critically impacts human health and the environment. One of natural process for cleaning up aerosols and air pollutants is rain. Raindrops absorb aerosols as they fall through the air, yet release aerosols back to atmosphere as they evaporate. However, it remains unclear how particle dynamics within a droplet affect the production of aerosols during evaporation. Using acoustic levitation, we experimentally investigate the collective dynamics of glass microspheres inside rotating, evaporating drops. The levitated drops can easily rotate at rates up to 30 Hz through feedback with the acoustic field. We find that microparticles exhibit distinct self-assembly dynamics, from "bands" along the equator of the axis of rotation to "sea ice" accumulated at the north and south poles, to "conveyor belts" of particles transported along the drop surface. To further understand these phenomena, we perform numerical simulations of particles in a rotating fluid with centrifugal force, Coriolis force, gravity, buoyancy, Stokes drag, and hydrostatic force due to centrifugal pressure gradient. Simulation results show that different dynamics of microspheres are determined by the angle between gravity and angular velocity, and the density difference between microparticles and water. |
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