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A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Non-Newtonian and Complex Fluids".

Deadline for manuscript submissions: closed (31 March 2020) | Viewed by 53851

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Prof. Dr. Laura A. Miller

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Departments of Biology and Mathematics, University of North Carolina, Chapel Hill, NC 27599, USA
Interests: mathematical biology; computational fluid dynamics; biomechanics
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Prof. Dr. Arvind Santhanakrishnan

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School of Mechanical & Aerospace Engineering, Oklahoma State University, 201 General Academic Building, Stillwater, OK 74078, USA
Interests: experimental fluid dynamics; biomechanics; bio-inspired design
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Dear Colleagues,

The biological world is replete with countless examples of fluid dynamics problems including pumping of blood by the heart, swimming in water and mucus, flying on scales from tiny insects to large birds, filtering through bristled appendages and other porous structures, and drag reduction through reconfiguration. Recent advancements in computational and experimental fluid dynamics have enabled researchers to efficiently explore biological problems that involve moving elastic boundaries across orders of magnitude in scale. Efforts to understand the dynamics of these types of problems through mathematical analysis, laboratory experiments, and numerical modeling is a rapidly expanding area of fluid mechanics. Simplified mathematical and physical models of these systems also have the potential to inform the design of robots and autonomous underwater and aerial vehicles. This Special Issue of Fluids is dedicated to the recent advances in the mathematical, numerical and physical modeling of problems in biological fluid dynamics with applications to bio-inspired design.

Prof. Laura A. Miller
Dr. Arvind Santhanakrishnan
Guest Editors

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Keywords

biofluids
biomechanics
computational fluid dynamics
biomimetics
bio-inspired design
mathematical biology

Published Papers (11 papers)

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Research

15 pages, 4717 KiB

Open AccessEditor’s ChoiceArticle

A Numerical Study of Metachronal Propulsion at Low to Intermediate Reynolds Numbers

by Shawtaroh Granzier-Nakajima, Robert D. Guy and Calvin Zhang-Molina

Fluids 2020, 5(2), 86; https://doi.org/10.3390/fluids5020086 - 31 May 2020

Cited by 17 | Viewed by 2951

Abstract

Inspired by the forward swimming of long-tailed crustaceans, we study an underwater propulsion mechanism for a swimming body with multiple rigid paddles attached underneath undergoing cycles of power and return strokes with a constant phase-difference between neighboring paddles, a phenomenon known as metachronal propulsion. To study how inter-paddle phase-difference affects flux production, we develop a computational fluid dynamics model and a numerical algorithm based on the immersed boundary method, which allows us to simulate metachronal propulsion at Reynolds numbers (RE) ranging from close to 0 to about 100. Our main finding is that the highest average flux is generated when nearest-neighbor paddles maintain an approximate 20%–25% phase-difference with the more posterior paddle leading the cycle; this result is independent of stroke frequency across the full range of RE considered here. We also find that the optimal paddle spacing and the number of paddles depend on RE; we see a qualitative transition in the dynamics of flow generated by metachronal propulsion as RE rises above 80. Roughly speaking, in terms of average flux generation, a tight paddle spacing is preferred when RE is less than 10, but a wider spacing becomes clearly favored when RE is close to or above 100. In terms of efficiency of flux generation, at RE 0.1 the maximum efficiency occurs at two paddles, and the efficiency decreases as the number of paddles increases. At RE 100 the efficiency increases as the number of paddles increases, and it appears to saturate by eight paddles, whereas using four paddles is a good tradeoff for both low and intermediate RE. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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18 pages, 2600 KiB

Open AccessArticle

Interpreting the Spatial-Temporal Structure of Turbulent Chemical Plumes Utilized in Odor Tracking by Lobsters

by Kyle W. Leathers, Brenden T. Michaelis and Matthew A. Reidenbach

Fluids 2020, 5(2), 82; https://doi.org/10.3390/fluids5020082 - 24 May 2020

Cited by 10 | Viewed by 3511

Abstract

Olfactory systems in animals play a major role in finding food and mates, avoiding predators, and communication. Chemical tracking in odorant plumes has typically been considered a spatial information problem where individuals navigate towards higher concentration. Recent research involving chemosensory neurons in the spiny lobster, Panulirus argus, show they possess rhythmically active or ‘bursting’ olfactory receptor neurons that respond to the intermittency in the odor signal. This suggests a possible, previously unexplored olfactory search strategy that enables lobsters to utilize the temporal variability within a turbulent plume to track the source. This study utilized computational fluid dynamics to simulate the turbulent dispersal of odorants and assess a number of search strategies thought to aid lobsters. These strategies include quantification of concentration magnitude using chemosensory antennules and leg chemosensors, simultaneous sampling of water velocities using antennule mechanosensors, and utilization of antennules to quantify intermittency of the odorant plume. Results show that lobsters can utilize intermittency in the odorant signal to track an odorant plume faster and with greater success in finding the source than utilizing concentration alone. However, the additional use of lobster leg chemosensors reduced search time compared to both antennule intermittency and concentration strategies alone by providing spatially separated odorant sensors along the body. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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17 pages, 1085 KiB

Open AccessArticle

Dynamic Analysis and Design Optimization of a Drag-Based Vibratory Swimmer

by Sevak Tahmasian, Arsam Jafaryzad, Nicolas L. Bulzoni and Anne E. Staples

Fluids 2020, 5(1), 38; https://doi.org/10.3390/fluids5010038 - 22 Mar 2020

Cited by 5 | Viewed by 2587

Abstract

Many organisms achieve locomotion via reciprocal motions. This paper presents the dynamic analysis and design optimization of a vibratory swimmer with asymmetric drag forces and fluid added mass. The swimmer consists of a floating body with an oscillatory mass inside. One-dimensional oscillations of the mass cause the body to oscillate with the same frequency as the mass. An asymmetric rigid fin attached to the bottom of the body generates asymmetric hydrodynamic forces, which drive the swimmer either backward or forward on average, depending on the orientation of the fin. The equation of motion of the system is a time-periodic, piecewise-smooth differential equation. We use simulations to determine the hydrodynamic forces acting on the fin and averaging techniques to determine the dynamic response of the swimmer. The analytical results are found to be in good agreement with vibratory swimmer prototype experiments. We found that the average unidirectional speed of the swimmer is optimized if the ratio of the forward and backward drag coefficients is minimized. The analysis presented here can aid in the design and optimization of bio-inspired and biomimetic robotic swimmers. A magnetically controlled microscale vibratory swimmer like the one described here could have applications in targeted drug delivery. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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17 pages, 2658 KiB

Open AccessArticle

Suction Flows Generated by the Carnivorous Bladderwort Utricularia—Comparing Experiments with Mechanical and Mathematical Models

by Krizma Singh, Roberto C. Reyes, Gabriel Campa, Jr., Matthew D. Brown, Fatima Hidalgo, Otto Berg and Ulrike K. Müller

Fluids 2020, 5(1), 33; https://doi.org/10.3390/fluids5010033 - 15 Mar 2020

Cited by 7 | Viewed by 4283

Abstract

Suction feeding is a well-understood feeding mode among macroscopic aquatic organisms. The little we know about small suction feeders from larval fish suggests that small suction feeders are not effective. Yet bladderworts, an aquatic carnivorous plant with microscopic underwater traps, have strong suction performances despite having the same mouth size as that of fish larvae. Previous experimental studies of bladderwort suction feeding have focused on the solid mechanics of the trap door’s opening mechanism rather than the mechanics of fluid flow. As flows are difficult to study in small suction feeders due to their small size and brief event durations, we combine flow visualization on bladderwort traps with measurements on a mechanical, dynamically scaled model of a suction feeder. We find that bladderwort traps generate flows that are more similar to the inertia-dominated flows of adult fish than the viscosity-dominated flows of larval fish. Our data further suggest that axial flow transects through suction flow fields, often used in biological studies to characterize suction flows, are less diagnostic of the relative contribution of inertia versus viscosity than transverse transects. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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10 pages, 887 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Metachronal Swimming with Rigid Arms near Boundaries

by Rintaro Hayashi and Daisuke Takagi

Fluids 2020, 5(1), 24; https://doi.org/10.3390/fluids5010024 - 14 Feb 2020

Cited by 15 | Viewed by 2415

Abstract

Various organisms such as crustaceans use their appendages for locomotion. If they are close to a confining boundary then viscous as opposed to inertial effects can play a central role in governing the dynamics. To study the minimal ingredients needed for swimming without inertia, we built an experimental system featuring a robot equipped with a pair of rigid slender arms with negligible inertia. Our results show that directing the arms to oscillate about the same time-averaged orientation produces no net displacement of the robot each cycle, regardless of any phase delay between the oscillating arms. The robot is able to swim if the arms oscillate asynchronously around distinct orientations. The measured displacement over time matches well with a mathematical model based on slender-body theory for Stokes flow. Near a confining boundary, the robot with no net displacement every cycle showed similar behavior, while the swimming robot increased in speed closer to the boundary. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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18 pages, 3553 KiB

Open AccessEditor’s ChoiceArticle

Fluid Dynamics of Ballistic Strategies in Nematocyst Firing

by Christina Hamlet, Wanda Strychalski and Laura Miller

Fluids 2020, 5(1), 20; https://doi.org/10.3390/fluids5010020 - 08 Feb 2020

Cited by 8 | Viewed by 8794

Abstract

Nematocysts are stinging organelles used by members of the phylum Cnidaria (e.g., jellyfish, anemones, hydrozoans) for a variety of important functions including capturing prey and defense. Nematocysts are the fastest-known accelerating structures in the animal world. The small scale (microns) coupled with rapid acceleration (in excess of 5 million g) present significant challenges in imaging that prevent detailed descriptions of their kinematics. The immersed boundary method was used to numerically simulate the dynamics of a barb-like structure accelerating a short distance across Reynolds numbers ranging from 0.9–900 towards a passive elastic target in two dimensions. Results indicate that acceleration followed by coasting at lower Reynolds numbers is not sufficient for a nematocyst to reach its target. The nematocyst’s barb-like projectile requires high accelerations in order to transition to the inertial regime and overcome the viscous damping effects normally encountered at small cellular scales. The longer the barb is in the inertial regime, the higher the final velocity of the projectile when it touches its target. We find the size of the target prey does not dramatically affect the barb’s approach for large enough values of the Reynolds number, however longer barbs are able to accelerate a larger amount of surrounding fluid, which in turn allows the barb to remain in the inertial regime for a longer period of time. Since the final velocity is proportional to the force available for piercing the membrane of the prey, high accelerations that allow the system to persist in the inertial regime have implications for the nematocyst’s ability to puncture surfaces such as cellular membranes or even crustacean cuticle. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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15 pages, 5241 KiB

Open AccessEditor’s ChoiceArticle

Stability of Soft Magnetic Helical Microrobots

by Kiarash Samsami, Seyed Amir Mirbagheri, Farshad Meshkati and Henry Chien Fu

Fluids 2020, 5(1), 19; https://doi.org/10.3390/fluids5010019 - 05 Feb 2020

Cited by 9 | Viewed by 3094

Abstract

Nano/microrobotic swimmers have many possible biomedical applications such as drug delivery and micro-manipulation. This paper examines one of the most promising classes of these: rigid magnetic microrobots that are propelled through bulk fluid by rotation induced by a rotating magnetic field. Propulsion corresponds to steadily rotating and translating solutions of the dynamics of such microrobots that co-rotate with the magnetic field. To be observed in experiments and be amenable to steering control, such solutions must also be stable to perturbations. In this paper, we analytically derive a criterion for the stability of such steadily rotating solutions for a microrobot made of soft magnetic materials, which have a magnetization that depends on the applied field. This result generalizes previous stability criteria we obtained for microrobots with a permanent magnetization. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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20 pages, 4853 KiB

Open AccessFeature PaperArticle

Dynamics of Swimmers in Fluids with Resistance

by Cole Jeznach and Sarah D. Olson

Fluids 2020, 5(1), 14; https://doi.org/10.3390/fluids5010014 - 19 Jan 2020

Cited by 6 | Viewed by 3031

Abstract

Micro-swimmers such as spermatozoa are able to efficiently navigate through viscous fluids that contain a sparse network of fibers or other macromolecules. We utilize the Brinkman equation to capture the fluid dynamics of sparse and stationary obstacles that are represented via a single resistance parameter. The method of regularized Brinkmanlets is utilized to solve for the fluid flow and motion of the swimmer in 2-dimensions when assuming the flagellum (tail) propagates a curvature wave. Extending previous studies, we investigate the dynamics of swimming when varying the resistance parameter, head or cell body radius, and preferred beat form parameters. For a single swimmer, we determine that increased swimming speed occurs for a smaller cell body radius and smaller fluid resistance. Progression of swimmers exhibits complex dynamics when considering hydrodynamic interactions; attraction of two swimmers is a robust phenomenon for smaller beat amplitude of the tail and smaller fluid resistance. Wall attraction is also observed, with a longer time scale of wall attraction with a larger resistance parameter. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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18 pages, 1105 KiB

Open AccessArticle

Viscosity-Enhanced Fluid Drift around Hairy Structures

by Seyoung Joung, Hong Ki Lee and Daegyoum Kim

Fluids 2020, 5(1), 5; https://doi.org/10.3390/fluids5010005 - 03 Jan 2020

Cited by 3 | Viewed by 2902

Abstract

Hairy structures in nature function to sense smells and capture nutrients from surrounding fluid. Motivated by the complicated fluid transport processes observed in biological hairy structures, we numerically investigate the dynamics of fluid particles around multiple solid objects moving in a quiescent fluid, [...] Read more.

R e = 1

–100). The behavior of fluid particles entrained by a moving cylinder array is analyzed by tracking particle trajectories and computing the drift volume, which indicates the amount of fluid particles transported by the moving cylinders. Hydrodynamic blockage of gaps within the cylinder array, which arises from the overlap of shear layers due to viscous diffusion, is critical in determining the overall fluid particle dynamics. As the number of cylinders increases, the deformation of the material line composed of fluid particles and the magnitude of the resultant drift volume show consistent patterns, despite undergoing drastic changes, and they converge to a specific configuration and magnitude, respectively. This study shows that visualization and quantification of collective fluid transport by multiple solid bodies are important to evaluate the efficiency of fluid transport for a collection of multiple bodies and to find its optimal configuration. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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43 pages, 25327 KiB

Open AccessArticle

Naut Your Everyday Jellyfish Model: Exploring How Tentacles and Oral Arms Impact Locomotion

by Jason G. Miles and Nicholas A. Battista

Fluids 2019, 4(3), 169; https://doi.org/10.3390/fluids4030169 - 10 Sep 2019

Cited by 20 | Viewed by 16042

Abstract

Jellyfish are majestic, energy-efficient, and one of the oldest species that inhabit the oceans. It is perhaps the second item, their efficiency, that has captivated scientists for decades into investigating their locomotive behavior. Yet, no one has specifically explored the role that their tentacles and oral arms may have on their potential swimming performance. We perform comparative in silico experiments to study how tentacle/oral arm number, length, placement, and density affect forward swimming speeds, cost of transport, and fluid mixing. An open source implementation of the immersed boundary method was used (IB2d) to solve the fully coupled fluid–structure interaction problem of an idealized flexible jellyfish bell with poroelastic tentacles/oral arms in a viscous, incompressible fluid. Overall tentacles/oral arms inhibit forward swimming speeds, by appearing to suppress vortex formation. Nonlinear relationships between length and fluid scale (Reynolds Number) as well as tentacle/oral arm number, density, and placement are observed, illustrating that small changes in morphology could result in significant decreases in swimming speeds, in some cases by upwards of 80–90% between cases with or without tentacles/oral arms. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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18 pages, 2455 KiB

Open AccessArticle

Detailed Research on the Turbulent Kinetic Energy’s Distribution in Fishways in Reference to the Bolt Fishway

by Marta Puzdrowska and Tomasz Heese

Fluids 2019, 4(2), 64; https://doi.org/10.3390/fluids4020064 - 02 Apr 2019

Cited by 5 | Viewed by 3269

Abstract

Turbulent kinetic energy (TKE) and its distribution and volume remain—with the exception of flow velocity—the most important cause of the low efficiency of fish passes. Thus, it is important to define the reasons and mechanisms that explain the distribution of characteristic features of this parameter, as presented in the paper. This publication presents the spatial distribution of TKE for two models of bolt-type fishways. The paper shows details related to characteristic features of TKE distribution and intensity scale in a bolt fishway. The presented research results for the bolt fishway were obtained from laboratory tests using a physical model. Measurements were taken of three temporary components of flow velocity in the indicated measurement sections. It was established that differences in the TKE volume and distribution are a consequence of the state of the stream that leaves the slot’s section or the orifice’s section. This state is defined by the determination of the stream’s potential. A low potential results in high TKE values in the area of the main flow. Thus, considering various structural features of fish passes, one can assert that the potential remains a characteristic feature attributable to a particular type of facility. Full article

(This article belongs to the Special Issue Advances in Biological Flows and Biomimetics)

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