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Fluids
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Hydrodynamics of Swimming
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Hydrodynamics of Swimming

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Geophysical and Environmental Fluid Mechanics".

Deadline for manuscript submissions: closed (1 November 2021) | Viewed by 13047

Special Issue Editors

Prof. Dr. Sean P. Colin

E-Mail Website
Guest Editor
1. Marine Biology, Roger Williams University, Bristol, RI 02809, USA
2. Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA
Interests: animal–fluid interactions; functional morphology; plankton propulsion; predator–prey interactions
Prof. Dr. John H. Costello

E-Mail Website
Guest Editor
1. Biology Department, Providence College, Providence, RI 02918, USA
2. Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA
Interests: zooplankton ecology; animal design; organism–fluid interactions

Special Issue Information

Dear Colleagues,

For a long time, the study of the hydrodynamics of swimming animals has been limited by our ability to quantify and calculate essential body–fluid interactions around propulsive elements and, as a result, has largely been dependent on a few critical models to predict thrust on the basis of trailing wakes. Relatively recent advances have enabled researchers to quantify and predict flow adjacent to important propulsive elements and to calculate variables, such as pressure, that reveal how animals manipulate hydrodynamics for effective, efficient swimming.

This Special Issue of Fluids is dedicated to recent advances using experimental observations or computational techniques that are contributing to a new and more in-depth understanding of the hydrodynamics of swimming animals.

Prof. Dr. Sean P. Colin
Prof. Dr. John H. Costello
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • propulsion
  • thrust
  • flexible propulsors
  • vorticity
  • pressure fields
  • suction-thrust

Published Papers (5 papers)

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Research

11 pages, 4941 KiB  
Article
Velocity Field Measurements of the California Sea Lion Propulsive Stroke Using Bubble PIV
by Gino Perrotta, Frank E. Fish, Danielle S. Adams, Ariel M. Leahy, Abigal M. Downs and Megan C. Leftwich
Fluids 2022, 7(1), 3; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids7010003 - 22 Dec 2021
Viewed by 2409
Abstract
California sea lions are among the most agile of swimming mammals. Most marine mammals swim with their hind appendages—flippers or flukes, depending on the species—whereas sea lions use their foreflippers for propulsion and maneuvering. The sea lion’s propulsive stroke generates thrust by forming [...] Read more.
California sea lions are among the most agile of swimming mammals. Most marine mammals swim with their hind appendages—flippers or flukes, depending on the species—whereas sea lions use their foreflippers for propulsion and maneuvering. The sea lion’s propulsive stroke generates thrust by forming a jet between the flippers and the body and by dragging a starting vortex along the suction side of the flipper. Prior experiments using robotic flippers have shown these mechanisms to be possible, but no flow measurements around live sea lions previously existed with which to compare. In this study, the flow structures around swimming sea lions were observed using an adaptation of particle imaging velocimetry. To accommodate the animals, it was necessary to use bubbles as seed particles and sunlight for illumination. Three trained adult California sea lions were guided to swim through an approximately planar sheet of bubbles in a total of 173 repetitions. The captured videos were used to calculate bubble velocities, which were processed to isolate and inspect the flow velocities caused by the swimming sea lion. The methodology will be discussed, and measured flow velocities will be presented. Full article
(This article belongs to the Special Issue Hydrodynamics of Swimming)
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18 pages, 11784 KiB  
Article
High-Efficiency Can Be Achieved for Non-Uniformly Flexible Pitching Hydrofoils via Tailored Collective Interactions
by Melike Kurt, Amin Mivehchi and Keith Moored
Fluids 2021, 6(7), 233; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6070233 - 25 Jun 2021
Cited by 10 | Viewed by 2362
Abstract
New experiments examine the interactions between a pair of three-dimensional (AR = 2) non-uniformly flexible pitching hydrofoils through force and efficiency measurements. It is discovered that the collective efficiency is improved when the follower foil has a nearly out-of-phase synchronization with [...] Read more.
New experiments examine the interactions between a pair of three-dimensional (AR = 2) non-uniformly flexible pitching hydrofoils through force and efficiency measurements. It is discovered that the collective efficiency is improved when the follower foil has a nearly out-of-phase synchronization with the leader and is located directly downstream with an optimal streamwise spacing of X*=0.5. The collective efficiency is further improved when the follower operates with a nominal amplitude of motion that is 36% larger than the leader’s amplitude. A slight degradation in the collective efficiency was measured when the follower was slightly-staggered from the in-line arrangement where direct vortex impingement is expected. Operating at the optimal conditions, the measured collective efficiency and thrust are ηC=62% and CT,C=0.44, which are substantial improvements over the efficiency and thrust of ηC=29% and CT,C=0.16 of two fully-rigid foils in isolation. This demonstrates the promise of achieving high-efficiency with simple purely pitching mechanical systems and paves the way for the design of high-efficiency bio-inspired underwater vehicles. Full article
(This article belongs to the Special Issue Hydrodynamics of Swimming)
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13 pages, 3134 KiB  
Article
Numerical Simulation of Self-Propelled Steady Jet Propulsion at Intermediate Reynolds Numbers: Effects of Orifice Size on Animal Jet Propulsion
by Houshuo Jiang
Fluids 2021, 6(6), 230; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6060230 - 20 Jun 2021
Cited by 6 | Viewed by 2200
Abstract
Most marine jet-propelled animals have low swimming efficiencies and relatively small jet orifices. Motivated by this, the present computational fluid dynamics study simulates the flow for a jet-propelled axisymmetric body swimming steadily at intermediate Reynolds numbers of order 1–1000. Results show that swimming-imposed [...] Read more.
Most marine jet-propelled animals have low swimming efficiencies and relatively small jet orifices. Motivated by this, the present computational fluid dynamics study simulates the flow for a jet-propelled axisymmetric body swimming steadily at intermediate Reynolds numbers of order 1–1000. Results show that swimming-imposed flow field, drag coefficients, swimming efficiencies, and performance index (a metric comparing swimming speeds sustained by differently sized orifices ejecting the same volume flow rate) all depend strongly on orifice size, and orifice size affects the configuration of oppositely signed body vorticity and jet vorticity, thereby affecting wake and efficiency. As orifice size decreases, efficiencies decrease considerably, while performance index increases substantially, suggesting that, for a given jet volume flow rate, a smaller orifice supports faster swimming than a larger one does, albeit at reduced efficiency. These results support the notion that most jet-propelled animals having relatively small jet orifices may be an adaptation to deal with the physical constraint of limited total volume of water available for jetting, while needing to compete for fast swimming. Finally, jet orifice size is discussed regarding the role of jet propulsion in jet-propelled animal ecology, particularly for salps that use two relatively large siphons to respectively draw in and expel water. Full article
(This article belongs to the Special Issue Hydrodynamics of Swimming)
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17 pages, 3926 KiB  
Article
A Computational Model for Tail Undulation and Fluid Transport in the Giant Larvacean
by Alexander P. Hoover, Joost Daniels, Janna C. Nawroth and Kakani Katija
Fluids 2021, 6(2), 88; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6020088 - 20 Feb 2021
Cited by 4 | Viewed by 2317
Abstract
Flexible propulsors are ubiquitous in aquatic and flying organisms and are of great interest for bioinspired engineering. However, many animal models, especially those found in the deep sea, remain inaccessible to direct observation in the laboratory. We address this challenge by conducting an [...] Read more.
Flexible propulsors are ubiquitous in aquatic and flying organisms and are of great interest for bioinspired engineering. However, many animal models, especially those found in the deep sea, remain inaccessible to direct observation in the laboratory. We address this challenge by conducting an integrative study of the giant larvacean, an invertebrate swimmer and “fluid pump” of the mesopelagic zone. We demonstrate a workflow involving deep sea robots, advanced imaging tools, and numerical modeling to assess the kinematics and resulting fluid transport of the larvacean’s beating tail. A computational model of the tail was developed to simulate the local fluid environment and the tail kinematics using embedded passive (elastic) and active (muscular) material properties. The model examines how varying the extent of muscular activation affects the resulting kinematics and fluid transport rates. We find that muscle activation in two-thirds of the tail’s length, which corresponds to the observed kinematics in giant larvaceans, generates a greater average downstream flow speed than other designs with the same power input. Our results suggest that the active and passive material properties of the larvacean tail are tuned to produce efficient fluid transport for swimming and feeding, as well as provide new insight into the role of flexibility in biological propulsors. Full article
(This article belongs to the Special Issue Hydrodynamics of Swimming)
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12 pages, 5509 KiB  
Article
Decoding the Relationships between Body Shape, Tail Beat Frequency, and Stability for Swimming Fish
by Alexander P. Hoover and Eric Tytell
Fluids 2020, 5(4), 215; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids5040215 - 20 Nov 2020
Cited by 6 | Viewed by 2723
Abstract
As fish swim through a fluid environment, they must actively use their fins in concert to stabilize their motion and have a robust form of locomotion. However, there is little knowledge of how these forces act on the fish body. In this study, [...] Read more.
As fish swim through a fluid environment, they must actively use their fins in concert to stabilize their motion and have a robust form of locomotion. However, there is little knowledge of how these forces act on the fish body. In this study, we employ a 3D immersed boundary model to decode the relationship between roll, pitch, and yaw of the fish body and the driving forces acting on flexible fish bodies. Using bluegill sunfish as our representative geometry, we first examine the role of an actuating torque on the stability of the fish model, with a torque applied at the head of the unconstrained fish body. The resulting kinematics is a product of the passive elasticity, fluid forces, and driving torque. We then examine a constrained model to understand the role that fin geometry, body elasticity, and frequency play on the range of corrective forces acting on the fish. We find non-monotonic behavior with respect to frequency, suggesting that the effective flexibility of the fins play an important role in the swimming performance. Full article
(This article belongs to the Special Issue Hydrodynamics of Swimming)
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