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| Author | : Xiaoning Shen |
| Publisher | : |
| Total Pages | : 147 |
| Release | : 2013 |
| Genre | : |
| ISBN | : |
| Author | : On Shun Pak |
| Publisher | : |
| Total Pages | : 172 |
| Release | : 2013 |
| Genre | : |
| ISBN | : 9781303194610 |
Life under the microscope is significantly different from our experiences in the macroscopic world. Inertial effects, which govern motion at the macroscopic world, become subdominant to viscous forces at small length scales. The Reynolds number (Re) quantifies the relative importance of inertial to viscous forces. Microorganisms, such as bacteria and spermatozoa, inhabit environments with typical Re between 10̄̄−5 and 10−2. The absence of inertia imposes stringent constraints on the types of effective locomotion strategies. This also poses a fundamental challenge in designing synthetic swimmers and fluid transport systems at microscopic scales. Interestingly, microorganisms have evolved diverse strategies to achieve locomotion. This thesis is devoted to studying the fluid mechanics of biological and synthetic locomotion at low Reynolds number under three themes: swimming microorganisms, synthetic locomotion, and locomotion in complex fluids. The first theme focuses on using different idealized hydrodynamic models to study the swimming of microorganisms. Under this theme, we extend the classical Taylor's swimming sheet model to analyze the unsteady inertial effects in flagellar swimming. We also present a hydrodynamic investigation of an interesting double-wave structure observed in insect sperm flagella. We turn our attention to synthetic locomotion in the second theme. Different physical mechanisms are explored to design synthetic micro-swimmers, which have many potential biomedical applications, such as microsurgery and targeted drug delivery systems. Specifically, we exploit elasticity and extensibility of a body to design locomotion strategies. Finally, the third theme concerns locomotion in complex fluids. Most biological fluids are indeed polymeric and hence display non-Newtonian rheological properties. We investigate the idea of taking advantage of the nonlinear rheological properties of a complex fluid to enable locomotion otherwise impossible in a Newtonian fluid. Simple mechanisms are designed to exploit the non-Newtonian stresses for micropropulsion and micropumping. The results are also applied to developing a microrheological technique based on information from locomotion.
| Author | : Shahrzad Hossein Yazdi |
| Publisher | : |
| Total Pages | : |
| Release | : 2016 |
| Genre | : |
| ISBN | : |
Locomotion of microorganisms plays a vital role in most of their biological processes. In many of these processes, microorganisms are exposed to complex fluids while swimming in confined domains, such as spermatozoa in mucus of mammalian reproduction tracts or bacteria in extracellular polymeric matrices during biofilm formation. A better understanding of the hydrodynamic interaction of a motile microswimmer with a boundary in a viscoelastic fluid is crucial to elucidate many biological processes, such as adhesion of bacterial cells during the formation of microbial biofilms. In the recent years, the swimming of motile microorganisms in complex fluids has received significant attention. It has been shown that the viscoelasticity of the ambient fluid alters the swimming speed and efficiency of a single microorganism as well as a population of motile cells, depending on the rheological properties of the background fluid and the swimmers' propulsion mechanism. However, the majority of these studies assumed the fluid environment to be an unbounded domain. Therefore, the boundary induced effects, which are ubiquitous in microorganisms' natural habitat, on their swimming behavior in complex fluids are poorly understood. In this dissertation, we analytically investigate the combined effect of background fluid elasticity and confined environment on the swimming dynamics of a single microorganism. The self-propelled microorganism is simulated using a archetype model, known as "squirmer". In this model, the radial deformations of a self-propelled microswimmer is neglected and locomotion is merely induced via tangential motion of the swimmer's surface. We use a perturbation expansion to solve the Stokes equations in an Oldroyd-B fluid in the presence of a planar no-slip boundary. To this end, for the first time, the fully resolved solution of a confined squirmer in a Newtonian fluid in the absence of inertial forces is presented. The kinematics of swimming are examined for both two-dimensional and three-dimensional models and for the latter the investigation is extended to different types of boundaries. Our results are mainly presented through a phase portrait in swimming orientation and distance from the interface and are compared to that in a Newtonian fluid. We show that even in the limit of small Weissenberg number, the swimming dynamics significantly alters which leads to a dramatic increase in the residence time of the swimmer near the boundary.
| Author | : Stephen Childress |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 316 |
| Release | : 2012-08-14 |
| Genre | : Mathematics |
| ISBN | : 1461439973 |
This volume developed from a Workshop on Natural Locomotion in Fluids and on Surfaces: Swimming, Flying, and Sliding which was held at the Institute for Mathematics and its Applications (IMA) at the University of Minnesota, from June 1-5, 2010. The subject matter ranged widely from observational data to theoretical mechanics, and reflected the broad scope of the workshop. In both the prepared presentations and in the informal discussions, the workshop engaged exchanges across disciplines and invited a lively interaction between modelers and observers. The articles in this volume were invited and fully refereed. They provide a representative if necessarily incomplete account of the field of natural locomotion during a period of rapid growth and expansion. The papers presented at the workshop, and the contributions to the present volume, can be roughly divided into those pertaining to swimming on the scale of marine organisms, swimming of microorganisms at low Reynolds numbers, animal flight, and sliding and other related examples of locomotion.
| Author | : Saverio E. Spagnolie |
| Publisher | : Springer |
| Total Pages | : 449 |
| Release | : 2014-11-27 |
| Genre | : Science |
| ISBN | : 1493920650 |
This book serves as an introduction to the continuum mechanics and mathematical modeling of complex fluids in living systems. The form and function of living systems are intimately tied to the nature of surrounding fluid environments, which commonly exhibit nonlinear and history dependent responses to forces and displacements. With ever-increasing capabilities in the visualization and manipulation of biological systems, research on the fundamental phenomena, models, measurements, and analysis of complex fluids has taken a number of exciting directions. In this book, many of the world’s foremost experts explore key topics such as: Macro- and micro-rheological techniques for measuring the material properties of complex biofluids and the subtleties of data interpretation Experimental observations and rheology of complex biological materials, including mucus, cell membranes, the cytoskeleton, and blood The motility of microorganisms in complex fluids and the dynamics of active suspensions Challenges and solutions in the numerical simulation of biologically relevant complex fluid flows This volume will be accessible to advanced undergraduate and beginning graduate students in engineering, mathematics, biology, and the physical sciences, but will appeal to anyone interested in the intricate and beautiful nature of complex fluids in the context of living systems.
| Author | : David A. Gagnon |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2017 |
| Genre | : |
| ISBN | : |
Swimming microorganisms such as bacteria, spermatozoa, algae, and nematodes are critical to ubiquitous biological phenomena such as disease and infection, ecosystem dynamics, and mammalian fertilization. While there has been much scientific and practical interest in studying these swimmers in Newtonian (water-like) fluids, there are fewer systematic experimental studies on swimming through non-Newtonian (non-water-like) fluids with biologically-relevant mechanical properties. These organisms commonly swim through viscoelastic, structured, or shear-rate-dependent fluids, such as blood, mucus, and living tissues. Furthermore, the small length scales of these organisms dictate that their motion is dominated by viscous forces and inertia is negligible. Using rheology, microscopy, particle tracking, and image processing techniques, we examine the interaction of low Reynolds number swimmers and non-Newtonian fluids including viscoelastic, locally-anisotropic, and shear-thinning fluids. We then apply our understanding of locomotion to the study of the genetic disease Spinal Muscular Atrophy.
| Author | : David B. Dusenbery |
| Publisher | : Harvard University Press |
| Total Pages | : 449 |
| Release | : 2011-03-04 |
| Genre | : Science |
| ISBN | : 0674261674 |
Kermit the Frog famously said that it isn’t easy being green, and in Living at Micro Scale David Dusenbery shows that it isn’t easy being small—existing at the size of, say, a rotifer, a tiny multicellular animal just at the boundary between the visible and the microscopic. “Imagine,” he writes, “stepping off a curb and waiting a week for your foot to hit the ground.” At that scale, we would be small enough to swim inside the letter O in the word “rotifer.” What are the physical consequences of life at this scale? How do such organisms move, identify prey and predators and (if they’re so inclined) mates, signal to one another, and orient themselves? In clear and engaging prose, Dusenbery uses straightforward physics to demonstrate the constraints on the size, shape, and behavior of tiny organisms. While recounting the historical development of the basic concepts, he unearths a corner of microbiology rich in history, and full of lessons about how science does or does not progress. Marshalling findings from different fields to show why tiny organisms have some of the properties they are found to have, Dusenbery shows a science that doesn’t always move triumphantly forward, and is dependent to a great extent on accident and contingency.
| Author | : Heba Adil Allhibi |
| Publisher | : |
| Total Pages | : 104 |
| Release | : 2015 |
| Genre | : |
| ISBN | : |
The micoorganisms' entire bodies' movement in fluid media is called locomotion. The study of locomotion of live organisms is significant because of the existence of microorganisms that use flagella or cilia in human's body cells. The aim of this research is to study the classical Taylor's swimming sheet problem in complex fluids (Newtonian and non- Newtonian), which are the mixtures of two fluids with different physical properties. We applied a novel two-phase immersed boundary method to simulate the mixture-structure interactions, with a Multigrid preconditioned Krylov Subspace solver for the fluid equations. Our computational simulations agree well with the related analytical results in the literature for a single-phase fluid. Furthermore, our work indicates that the properties of the fluid mixture have a significant and nontrivial impact on the swimming behavior.
| Author | : Camille Duprat |
| Publisher | : Royal Society of Chemistry |
| Total Pages | : 498 |
| Release | : 2016 |
| Genre | : Science |
| ISBN | : 1849738130 |
An approachable introduction to low Reynolds number flows and elasticity for those new to the area across engineering, physics, chemistry and biology.
| Author | : Graham Taylor |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 433 |
| Release | : 2010-03-20 |
| Genre | : Science |
| ISBN | : 3642116337 |
The physical principles of swimming and flying in animals are intriguingly different from those of ships and airplanes. The study of animal locomotion therefore holds a special place not only at the frontiers of pure fluid dynamics research, but also in the applied field of biomimetics, which aims to emulate salient aspects of the performance and function of living organisms. For example, fluid dynamic loads are so significant for swimming fish that they are expected to have developed efficient flow control procedures through the evolutionary process of adaptation by natural selection, which might in turn be applied to the design of robotic swimmers. And yet, sharply contrasting views as to the energetic efficiency of oscillatory propulsion – especially for marine animals – demand a careful assessment of the forces and energy expended at realistic Reynolds numbers. For this and many other research questions, an experimental approach is often the most appropriate methodology. This holds as much for flying animals as it does for swimming ones, and similar experimental challenges apply – studying tethered as opposed to free locomotion, or studying the flow around robotic models as opposed to real animals. This book provides a wide-ranging snapshot of the state-of-the-art in experimental research on the physics of swimming and flying animals. The resulting picture reflects not only upon the questions that are of interest in current pure and applied research, but also upon the experimental techniques that are available to answer them.
