Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session A24: Microscale Flows: Streaming and Assembly |
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Chair: Anke Lindner, ESPCI Paris Room: Georgia World Congress Center B312 |
Sunday, November 18, 2018 8:00AM - 8:13AM |
A24.00001: Streaming-reinforced particle transport Tejaswin Parthasarathy, Fan Kiat Chan, Mattia Gazzola Motivated by drug-delivery applications, we investigate the capability of an 'active' body (master) to manipulate a 'passive' object (slave) purely via contactless flow-mediated mechanisms. We extend prior works on active--passive cylinder pairs by superimposing periodic oscillations to the master's linear motion. In a viscous fluid, such oscillations produce an additional viscous streaming field, which is leveraged for enhancing the slave transport. We see that superimposing oscillations robustly improves transport across a range of Reynolds numbers. Comparison with results without oscillations highlights the flow mechanisms at work, which we capitalize on to design (master) geometries for augmented transport. |
Sunday, November 18, 2018 8:13AM - 8:26AM |
A24.00002: How shape topology affects streaming flow topology Fan Kiat Chan, Tejaswin Parthasarathy, Mattia Gazzola Three-dimensional viscous streaming flows arising from spheroids are broadly understood, their counterparts from irregular shapes less so. Motivated by the gap in this understanding, we established a computational framework to investigate the streaming flow behavior associated with oscillating bodies of arbitrary shapes. We begin to bridge the aforementioned knowledge gap by exploring the effect of shape topology on streaming behavior. |
Sunday, November 18, 2018 8:26AM - 8:39AM |
A24.00003: Investigating the role of multiple body curvatures on viscous streaming dynamics Mattia Gazzola, Tejaswin Parthasarathy, Fan Kiat Chan Two-dimensional viscous streaming flows arising from shapes of constant curvature (plates and circular cylinders) have been well understood as a second-order effect. However, relatively little is known about such flows when object(s) of multiple curvatures are involved. Using an established computational framework, we investigate the role of body curvature in the streaming flow dynamics, exploring the possibility of multiple curvatures eliciting higher-order streaming terms and topological changes. |
Sunday, November 18, 2018 8:39AM - 8:52AM |
A24.00004: Steady Streaming flow induced by two oscillating parallel infinite plates Mohammad AlHamli, Satwindar Singh Sadhal Singular perturbation method was used to investigate the steady streaming flow pattern of a viscous fluid between two infinite parallel plates. The upper and the lower plates were allowed to oscillate with two different frequencies (ω1 and ω2),phase shift (φ1andφ2 )between the vertical and the lateral velocities of the two plates, and amplitudes of oscillations ( ε1a and ε2a) . Where a is the width of the microchannel. These assumptions can create two completely different frequency parameters (|M1|2 and |M2|2 ) for the upper and the lower plates. The frequency parameter |M|2 =ωa2/ν is the ratio channel width to the viscous length and it is assumed to be large, |M|2>>1 . When these two distinct steady streaming flows induced by the upper and the lower oscillating plates, interact with each other they create different steady streaming flow pattern. The resulting steady streaming can be used to optimize mixing or pumping of the sandwiched fluid in the microchannel. |
Sunday, November 18, 2018 8:52AM - 9:05AM |
A24.00005: Steady streaming rheology for Newtonian fluids Giridar Vishwanathan, Gabriel Juarez Steady streaming in microfluidic devices has received considerable attention over the past decade due to its applications in particle manipulation, cell trapping, and microscale mixing. In this work, we discuss experimental results on the use of steady streaming for rheology, with a focus on characterizing the kinematic viscosity of Newtonian liquids. An oscillatory flow field is setup in a microfluidic channel using an electroacoustic transducer over a range of frequencies . The resulting steady streaming flow around a cylindrical post is observed using stroboscopic and high-speed imaging of passive tracer particles on an inverted microscope. The velocity fields are acquired through particle tracking velocimetry methods. Features of the radial stream function profile, which serve as a measure of the dynamic response, are used to characterize the liquid as a function of excitation frequency and non-dimensional oscillation amplitude. |
Sunday, November 18, 2018 9:05AM - 9:18AM |
A24.00006: Effect of bending on sedimentation of two deformable microparticles Marek Bukowicki, Maria Ekiel-Jeżewska Due to fast development of manipulation and observation techniques in microfluids, the dynamics of deformable microparticles under gravity, or centrifuged, is becoming an interesting topic of research. One of basic problems is how two such objects interact hydrodynamically with each other, and are there any ordering effects. In our previous study we reported that two sedimenting microfilaments in a symmetric configuration initially oscillate and later converge to an aligned, horizontal configuration. Here we show that for this system, bending of microparticles is the crucial feature behind their alignment behavior. We show that two sedimenting elastic trumbbells, the simplest model of bending particles, are able to recover dynamics of elastic filaments. A model of elastic particles which cannot bend, two dumbbells, leads to very different dynamics: particles oscillate, repel each other and do not align. We propose mechanism responsible for observed alignment effect of two flexible particles. Additionally, stability of the alignment is examined and confirmed. We conclude that trumbbell model may accurately describe important features of moving microfilaments and other microparticles which can bend. |
Sunday, November 18, 2018 9:18AM - 9:31AM |
A24.00007: Hydrodynamic interactions of colloidal droplets and their self-assembly in a microfluidic channel Zhouyang Ge, Luca Brandt The recent experiment by Shen et al. (Adv. Sci. 3, 1600012, 2016) demonstrated the generation of micron-sized colloidal droplets and their subsequent self-assembly into dumbbells, triangles, etc., considered as building blocks of photonic materials, in a microfluidic channel. To understand the underlying hydrodynamic mechanism, hence better harnessing the process, we repeat the experiment numerically for 2-10 droplets, using the interface-correction level set/ghost fluid method (Ge et al. J. Comput. Phys. 353, 2018). As we vary the droplet initial position, the inflow condition, and the confinement, we find that their hydrodynamic interaction remains weak far from the channel inlet. Moreover, the dynamic rearrangement of the droplets is found to be mostly induced by the cross-stream migration, a 3D effect instead of the typical q2D dipolar flows. Our result is consistent with the theoretical analysis of Fouxon et al. (Phys. Rev. E. 96, 063110, 2017), suggesting that a highly non-uniform inflow condition is crucial for effective flow-assisted self-assemblies. |
Sunday, November 18, 2018 9:31AM - 9:44AM |
A24.00008: Dissipative particle dynamics simulations of protein-directed self-assembly of nanoparticles Chunhui Li, Xuewei Fu, Weihong (Katie) Zhong, Jin Liu The “shuttle effect” caused by the dissolution and migration of polysulfides during the charge-discharge process is believed to be one of the main reasons for rapid capacity fading and low Coulombic efficiency in lithium-sulfur batteries. Recently we have successfully designed and fabricated a protein-based nanofilter for effectively trapping polysulfides but facilitating the Li+ transport. The nanofilter with unique porous structures is formed through a protein-directed self-assembly process and the surfaces are functionalized by the protein residues. In this work through dissipative particle dynamics simulations, we systematically investigate the self-assembly process of protein-coated nanoparticles. Mimicking the experimental conditions, we explore the effects from the coating materials (gelatin or polymer), surface coating density and solvent environments (water or acetic acid/water mixture), on the resulting porous structures. Our results demonstrate that consistent with experimental observations the final structures are highly dependent on above conditions. The simulations may provide guidelines for further improvement of nanofilter and eventually lead to better performance of lithium-sulfur batteries. |
Sunday, November 18, 2018 9:44AM - 9:57AM |
A24.00009: Hydrodynamic flux-induced clustering of Janus particles in optical potential Luca Biancofiore, Masoumeh Mousavi, Sabareesh K. P. Velu, Agnese Callegari, Giovanni Volpe Self-organisation is one of the most important strategies used by many biological systems, such as bacteria growth colonies, for the development of functional and complex patterned structures. Biological systems inspired self-organisation offers opportunities to simplify processes and to develop next generation materials and devices for molecular electronics, photonics and nanotechnology. The ability of organisation is mainly driven by the mutual interactions of the individual components and highly mediated by the environment features. In this work, we demonstrate experimentally that a system of Janus particles (half gold coated silica particles) experiences an unusual clustering in presence of a smooth Gaussian optical potential and an immediate release when the optical potential is switched off. Through numerical simulations we show that the key ingredient of the underlying mechanism is the existence of a hydrodynamic flow induced by a temperature gradient generated by the light absorption of the Janus particles. The proposed model is further applied to the case of non-Janus particles (non-coated silica particles) and of mixed Janus and non-Janus particles and well agrees with experiments in both cases. |
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