Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session A23: Microscale Flows: Particles, Drops, Bubbles I |
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Chair: Daren Watson, Florida Polytechnic University Room: North 224 A |
Sunday, November 21, 2021 8:00AM - 8:13AM |
A23.00001: Hydrodynamically induced particle drift near corrugated surfaces Danielle L. Chase, Christina Kurzthaler, Howard A Stone We present an experimental and theoretical study of the sedimentation of spheres nearby corrugated surfaces, whose grooves are tilted with respect to the gravitational force. Our experiments show oscillatory, or zigzag, particle trajectories and an overall drift along the surface grooves. We develop an analytical perturbation theory for the hydrodynamic interactions between the sedimenting sphere and the corrugated surface and find agreement between our theory and experiments. The theoretical predictions further reveal that the interactions of the flows induced by the particle motion with the surface shapes generate local pressure gradients, which explain the observed oscillatory dynamics. Additionally, we demonstrate that this behavior is generic for various surface shapes, including rectangular, sinusoidal, and triangular grooves. Finally, we theoretically and experimentally quantify the particle drift as a function of the shape and wavelength of the corrugations and the particle size to identify the parameters which lead to an optimal transport of the particles. |
Sunday, November 21, 2021 8:13AM - 8:26AM |
A23.00002: Inertial Lift Velocities For Particles In Curvilinear Background Flow Samuel E Christensen, Marcus Roper Inertial lift forces are used within microfluidic particles to position, segregate, and sort particles and droplets. Previous theoretical results can accurately predict this phenomena in rectilinear flows but have avoided looking at curvilinear flows to avoid the unsteady terms and nonlinearity that arise. Here, we use asymptotic methods to construct a singularity approximation method for efficiently calculating inertial lift in curvilinear background flow. We will use our new theory to explore under what conditions particles will get trapped in cavity flow. |
Sunday, November 21, 2021 8:26AM - 8:39AM |
A23.00003: Computational modeling of adhesion-based cell sorting in label-free microfluidic platform Fatima Ezahra Chrit, Alan Liu, Avi Gupta, Todd Sulchek, Alexander Alexeev Identifying and isolating cells that express desired molecular surface markers is required in a variety of applications in the biological sciences, cell therapy, and medical diagnostics. We develop a biophysical approach for high-throughput and label-free sorting of cells by their affinity for target ligands by molecular surface markers. Our approach consists of a microchannel decorated with periodic skewed ridges and coated with adhesive molecules. We use computer simulations to examine the effects of specific and non-specific adhesion on cell trajectories. Our specific adhesion model captures the adhesion kinetics and accounts for the molecular binding/unbinding events due to specific interactions of adhesive molecules and corresponding ligands. We find that specific and non-specific adhesion lead to distinct parameters of cells trajectories such as cell interaction time with the ridge, which can be used to identify different types of cell interaction. Furthermore, cell trajectories are sensitive to adhesion level and therefore can be used to sort cells with different ligand expression. |
Sunday, November 21, 2021 8:39AM - 8:52AM |
A23.00004: Exact solutions for quantifying spreading of chemotactic and diffusiophoretic species under a hydrodynamic flow Henry C Chu, Stephen Garoff, Robert D Tilton, Aditya S Khair The transport of microorganisms by chemotaxis is described by the same "log-sensing" response as colloids undergoing diffusiophoresis, despite their completely different mechanistic origins. In this talk, we employ a recent macrotransport theory to analyze the advective-diffusive transport of a chemotactic or diffusiophoretic colloidal species in a uniform circular tube under a steady pressure-driven flow and transient solute gradient. We derive exact solutions to the macrotransport equation, enabling efficient quantification of the large parameter space in chemotactic/diffusiophoretic colloid transport. First, we show that while hydrodynamic flow enhances colloid spreading in most cases, it can reduce colloid spreading for strongly solute-repelled colloids. Second, the minimum spreading for strongly solute-repelled colloids occurs in the intermediate hydrodynamic flow regime, contrasting the minimum for solute-attracted colloids which is attained in the absence of a hydrodynamic flow. Third, the macrotransport theory predicts new regimes of anomalous diffusion with a hybrid, linear-log-sensing chemotactic model, which otherwise cannot be realized with the traditional log-sensing relation. |
Sunday, November 21, 2021 8:52AM - 9:05AM |
A23.00005: Particle manipulation using variable body-curvature viscous streaming in microfluidic devices Gabriel Juarez, Giridar Vishwanathan, Yashraj R Bhosale, Tejaswin Parthasarathy, Mattia Gazzola Viscous streaming refers to the rectified, steady flows that emerge when a liquid oscillates around an immersed micro-feature, typically a solid body or a bubble. The ability of such features to locally concentrate energy and stresses that produce strong inertial effects to which both the fluid and suspended particles respond within short length and time scales, rendering viscous streaming arguably the most efficient mechanism to exploit inertia at the microscale. Despite this potential, viscous streaming has been investigated in rather narrow conditions, mostly making use of bodies of uniform curvature (cylinders and spheres) for which the induced flow topologies are limited. Here, we demonstrate that a variable body-curvature approach in viscous streaming dramatically extends the range of accessible flow topologies and enables novel applications for particle manipulation. We show for the first time that numerically predicted streaming flows can be physically reproduced in microfluidic chambers. We demonstrate how these newly accessible flow topologies are used to enhance particle manipulation, such as filtering and separation, in compact, robust, tunable, and inexpensive microfluidic devices. |
Sunday, November 21, 2021 9:05AM - 9:18AM |
A23.00006: Modeling of DC-electrokinetic motion of colloidal cylinders in the vicinity of a wall Atakan Atay, Ali Beskok, Barbaros Cetin The electrokinetic behavior of the particles in a microchannel is widely investigated due to their potential use in microfluidic applications such as separation or characterization of bio-molecules, bacteria, self-assembly processes etc. In this study, DC-electrokinetic behavior of colloidal particles in the vicinity of a conducting/non-conducting planar boundary is investigated using an inhouse boundary element method based solver. The contribution of hydrodynamic drag, electrokinetic (both electrophoretic and dielectrophoretic), and colloidal forces (van der Waals and EDL) to overall particle velocity is assessed. The colloidal forces are calculated using prescribed relations obtained from the literature, and included in the model as external forces acting on the particles. The electrokinetic forces are obtained by integrating Maxwell stress tensor over particles' surfaces. Position and velocities of the particles along with resulting flow and electric fields are computed. Overall, results are compared with experimental observations and a general discussion regarding colloidal behavior is presented. |
Sunday, November 21, 2021 9:18AM - 9:31AM Not Participating |
A23.00007: Jetting with solid impurities Arnab Ghosh, Herman Wijshoff, Federico Toschi The formation of liquid jets is key to a number of applications, and most notably the formation of ink droplets in inkjet printing technology. Here we study how the presence of a small solid and mobile inclusion within the nozzle can lead to distortion of the jetting patterns. In order to be able to efficiently and accurately model the whole jetting process we employ a D3Q27 enhanced color gradient lattice Boltzmann method and we couple it with the momentum exchange bounce back technique in order to resolve the fluid-structure coupling between the solid particle and the fluid, including the wetting condition of the surface of the particle. With the present method we are able to reach realistic density ratios and viscosity values, thereby allowing for a side-by-side comparison with experiments. A number of numerical simulations were conducted by varying the shape, size, density, initial position and orientation of the particle inside the nozzle, in order to study the effects on the shape and speed of the jetting liquid. |
Sunday, November 21, 2021 9:31AM - 9:44AM |
A23.00008: Nonuniform collective dissolution of bubbles in regular pore networks Nerine Joewondo, Valeria Garbin, Ronny Pini We present the development of a mathematical model that describes the collective dissolution of gas bubbles in two-dimensional regular pore networks. The model is solved numerically by considering lattices with up to 169 bubbles and by evaluating the role of pore network connectivity, the presence of vacant sites and the initial bubble size distribution. In dense lattices, diffusive shielding prolongs the dissolution time of bubbles located in the centre of the lattice. The presence of the pore network enhances this effect, its strength depending on the network connectivity. For dense lattices, the extension of the final dissolution time relative to the unbounded (bulk) case can be approximated by the power-law function, Bk/l, where the constant l is the inter-bubble spacing, B is the number of bubbles and the exponent k depends on the network connectivity. Sparse bubble lattices experience decreased collective effect, as bubbles are further apart from each other. The results reveal that the evolution of the solute concentration field is both a consequence and a factor affecting bubble dissolution or growth. In fact, the geometry of the pore network perturbs the inward propagation of the dissolution front and generates vacant sites within the bubble lattice. This effect is enhanced by increasing the lattice size and decreasing the network connectivity, yielding strongly non-uniform solute concentration fields. The presence of an initial bubble size distribution leads to increasingly non-uniform dissolution time of the lattice, as a result of a solute concentration field that is nonuniform from the outset. |
Sunday, November 21, 2021 9:44AM - 9:57AM |
A23.00009: Flexible loops settling under gravity in a viscous fluid Yevgen Melikhov, Magdalena Gruziel-Słomka, Maria L Ekiel-Jeżewska For sedimenting flexible loops, recent stability analysis and numerical simulations, based on the elastica approximation (R. Waszkiewicz et al., J. Fluid Mech. 919 (2021) A14), predict modes of the dynamics different from the previous results obtained by applying the bead model with the pairwise-additive Rotne-Prager mobility matrices (M. Gruziel-Słomka et al., Soft Matter 15 (2019) 7262). Therefore, we revisit the problem using a more precise theoretical method - the bead model and a fast-convergent, higher order multipole expansion of the Stokes equations, corrected for lubrication and implemented in the HYDROMULTIPOLE numerical codes of a high accuracy. As in the previous studies, initially the loop is circular and tilted at a small angle with respect to the horizontal plane, and the dynamics is determined for a wide range of values of the elasto-gravitation number B. We recover the essential findings of the simpler Rotne-Prager approximation. We determine the approach of more stiff loops to a unique stationary orientation, dependent on B. For more flexible loops we find a very similar phase diagram of sedimentation periodic orbits, with one new dynamical mode that we describe in details. |
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