scholarly journals Strong confinement of active microalgae leads to inversion of vortex flow and enhanced mixing

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Debasmita Mondal ◽  
Ameya G Prabhune ◽  
Sriram Ramaswamy ◽  
Prerna Sharma
Keyword(s):  
Vortex Flow ◽  
Flow Fields ◽  
Theoretical Description ◽  
Fluid Mixing ◽  
Contact Friction ◽  
Parallel Plates ◽  
Method Of Images ◽  
Comprehensive Framework ◽  
Strong Confinement ◽  
The Stokes Equation

Microorganisms swimming through viscous fluids imprint their propulsion mechanisms in the flow fields they generate. Extreme confinement of these swimmers between rigid boundaries often arises in natural and technological contexts, yet measurements of their mechanics in this regime are absent. Here, we show that strongly confining the microalga Chlamydomonas between two parallel plates not only inhibits its motility through contact friction with the walls but also leads, for purely mechanical reasons, to inversion of the surrounding vortex flows. Insights from the experiment lead to a simplified theoretical description of flow fields based on a quasi-2D Brinkman approximation to the Stokes equation rather than the usual method of images. We argue that this vortex flow inversion provides the advantage of enhanced fluid mixing despite higher friction. Overall, our results offer a comprehensive framework for analyzing the collective flows of strongly confined swimmers.

scholarly journals Direct simulation on nonlinear thermokinetic phenomena due to induced-charge electroosmosis

2018 ◽  
Vol 855 ◽  
pp. 736-769 ◽  
Author(s):  
Hideyuki Sugioka
Keyword(s):  
Electric Field ◽  
Vortex Flow ◽  
Direct Simulation ◽  
General Phenomenon ◽  
Dielectric Particles ◽  
Self Consistent ◽  
Physics Simulation ◽  
Normal Diffusion ◽  
Consistent Manner ◽  
The Stokes Equation

Previously, we proposed a novel mechanism to produce a nonlinear thermokinetic phenomenon (NTKP) around a metal cylinder in an electrolyte on the basis of analytical discussion. In this study, by using a non-steady direct multi-physics simulation technique based on the Stokes equation coupled with the electroosmotic equation that considers normal diffusion, electrophoresis and thermal diffusion, we directly verify the NTKP and show that the original driving force is the excess ions pressed on the particle by the thermokinetic force and that the NTKP vortex flow around the particle is generated by the interaction between the excess ion and the electric field that is made by the excess ions and/or the Seebeck electric field due to the blocking boundary condition on the wall. Namely, two types of NTKP exist and they are explained in a self-consistent manner by our new theory. In addition, through the discussion of a dielectric particle, we show that the NTKP is a general phenomenon that can be found in both metal and dielectric particles. We believe that our findings provide a new unified viewpoint to understand complex thermokinetic phenomena near metal and dielectric particles.

scholarly journals Estimate of the superradiance spectrum in dispersive media

2020 ◽  
Vol 378 (2177) ◽  
pp. 20190236 ◽  
Author(s):  
Theo Torres
Keyword(s):  
Black Hole ◽  
Reflection Coefficient ◽  
Event Horizon ◽  
Vortex Flow ◽  
Theoretical Description ◽  
Dispersive Media ◽  
Next Generation ◽  
Rotating Black Hole ◽  
Analogue Gravity ◽  
The Many

In 2016, the Nottingham group detected the rotational superradiance effect. While this experiment demonstrated the robustness of the superradiance process, it still lacks a complete theoretical description due to the many effects at stage in the experiment. In this paper, we shine new light on this experiment by deriving an estimate of the reflection coefficient in the dispersive regime by means of a Wentzel–Kramers–Brillouin analysis. This estimate is used to evaluate the reflection coefficient spectrum of counter-rotating modes in the Nottingham experiment. Our finding suggests that the vortex flow in the superradiance experiment was not purely absorbing, contrary to the event horizon of a rotating black hole. While this result increases the gap between this experimental vortex flow and a rotating black hole, it is argued that it is in fact this gap that is the source of novel ideas. This article is part of a discussion meeting issue ‘The next generation of analogue gravity experiments’.

Non-spherical bubble behavior in vortex flow fields

2003 ◽  
Vol 32 (4-6) ◽  
pp. 281-290 ◽  
Author(s):  
J.-K. Choi ◽  
G. L. Chahine
Keyword(s):  
Vortex Flow ◽  
Flow Fields ◽  
Bubble Behavior ◽  
Spherical Bubble

Functional Assessment of an Anti-Abrasive Elbow for Particle-Laden Gas Flows

2005 ◽  
Vol 297-300 ◽  
pp. 2345-2350
Author(s):  
Young Jin Kim ◽  
H.S. Kim
Keyword(s):  
Functional Assessment ◽  
Power Plants ◽  
Vortex Flow ◽  
Flow Simulation ◽  
Simple Algorithm ◽  
Flow Fields ◽  
Particle Flow ◽  
Gas Flows ◽  
Governing Equations ◽  
Particle Flow Simulation

The characteristic of flow fields in elbow has been numerically studied to develop anti-abrasive elbows, which is typically equipped in coal-burning power plants, for conveying highvelocity particle-laden fluids. Specially, a vortex flow field in the pipe experiencing particle abrasion was formed and particle flow simulation was conducted. The governing equations for threedimensional, turbulent flow fields were discretized by FVM and solved by the SIMPLE algorithm.

scholarly journals Evaluation of yarn lateral deformation

2013 ◽  
Vol 13 (1) ◽  
pp. 17-21
Author(s):  
G. Krupincová ◽  
J. Drašarová ◽  
I. Mertová
Keyword(s):  
Fiber Material ◽  
Theoretical Description ◽  
Lateral Deformation ◽  
Parallel Plates ◽  
Cross Sectional ◽  
New Approach ◽  
Innovative Methods ◽  
Fabric Structure ◽  
Yarn Count ◽  
Sectional Analysis

Abstract The article focuses on a new approach for characterization and evaluation of lateral yarn deformation. A small review about theoretical description and measurement possibilities will be introduced. The evaluation of yarn compression will be done by three innovative methods (lateral deformation of yarn between two parallel plates, simulation of binding point of fabric, cross-sectional analysis of real fabric). The analysis of yarn deformation will be carried out for a set of samples in combination of fiber material, yarn count and given fabric structure.

scholarly journals 2D simulation and analysis of fluid flow between two sinusoidal parallel plates using lattice Bolzmann method

2013 ◽  
Vol 19 (3) ◽  
pp. 369-375
Author(s):  
Jelena Markovic ◽  
Natasa Lukic ◽  
Aleksandar Jokic ◽  
Bojana Ikonic ◽  
Jelena Ilic ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Heat Exchangers ◽  
Fluid Mixing ◽  
Turbulent Regime ◽  
Parallel Plates ◽  
Negative Effects ◽  
Flat Plates ◽  
2D Simulation ◽  
Dimensional Simulation ◽  
Boltzmann Method

In order to obtain a better heat transfer, it is important to enhance fluid mixing in heat exchangers. Since there are negative effects when heat exchangers are operating in turbulent regime (like significant pressure drop, increased size of the pump) it is necessary to apply the techniques which would provide better fluid mixing when heat exchangers are operating in laminar regime. Investigations have shown that use of sinusoidal instead of flat plates results in this effect. This study is a result of two dimensional simulation of fluid flow between two parallel sinusoidal plates. Simulation was done with the use of modified Openlb code, based on lattice Boltzmann method. Reynolds number was varied from 200 to 1000, and space between the plates was varied from 3cm to 5 cm. Results showed that sinusoidal plates enhance fluid mixing, especially with greater values of Re and smaller space between the plates, which is in agreement with previous investigations.

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