New Insights into Biological and Bioinspired Fluid Dynamics

A special issue of Biomimetics (ISSN 2313-7673).

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 5987

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Guest Editor
Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
Interests: fluid mechanics; biofluids; soft matter
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Special Issue Information

Dear Colleagues,

Fluids are key for sustaining biological life. The complex and often counterintuitive fluid dynamics of the animal world have served as a constant source of inspiration for researchers and engineers in the pursuit of a better understanding of biology and the development of novel devices and machines that can effectively replicate the behavior and function of animals. Among many others, examples of such systems include different modes of aquatic locomotion, flapping flight, flocking and swarming of animals, transport by flagella and cilia, sensory functions of the fish lateral line, hemodynamics, and flow in circulatory systems. Studies of these and other biological systems open up new and exciting opportunities for harnessing approaches and strategies inspired by nature to solve engineering problems.

This Special Issue aims to collect contributions that report on recent progress in biological and bioinspired fluid dynamics. We invite theoretical, computational, and experimental studies that focus on fundamental and applied aspects of fluid flows in biological and bioinspired systems and emphasize the diversity of their applications for designing novel biomimetic devices and machines.

Dr. Alexander Alexeev
Guest Editor

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 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

  • biofluids
  • aquatic locomotion
  • flapping flight
  • fluid–structure interactions
  • flow-induced vibrations
  • non-Newtonian fluids
  • complex fluids
  • active matter
  • boundary layer
  • flow separation
  • microfluidics
  • hemodynamics
  • cellular fluid mechanics
  • biosensors
  • collective behavior
  • schooling/flocking

Published Papers (5 papers)

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Research

24 pages, 17492 KiB  
Article
A Novel Hybrid Deep Learning Method for Predicting the Flow Fields of Biomimetic Flapping Wings
by Fujia Hu, Weebeng Tay, Yilun Zhou and Boocheong Khoo
Biomimetics 2024, 9(2), 72; https://doi.org/10.3390/biomimetics9020072 - 25 Jan 2024
Viewed by 1067
Abstract
The physics governing the fluid dynamics of bio-inspired flapping wings is effectively characterized by partial differential equations (PDEs). Nevertheless, the process of discretizing these equations at spatiotemporal scales is notably time consuming and resource intensive. Traditional PDE-based computations are constrained in their applicability, [...] Read more.
The physics governing the fluid dynamics of bio-inspired flapping wings is effectively characterized by partial differential equations (PDEs). Nevertheless, the process of discretizing these equations at spatiotemporal scales is notably time consuming and resource intensive. Traditional PDE-based computations are constrained in their applicability, which is mainly due to the presence of numerous shape parameters and intricate flow patterns associated with bionic flapping wings. Consequently, there is a significant demand for a rapid and accurate solution to nonlinear PDEs, to facilitate the analysis of bionic flapping structures. Deep learning, especially physics-informed deep learning (PINN), offers an alternative due to its great nonlinear curve-fitting capability. In the present work, a hybrid coarse-data-driven physics-informed neural network model (HCDD-PINN) is proposed to improve the accuracy and reliability of predicting the time evolution of nonlinear PDEs solutions, by using an order-of-magnitude-coarser grid than traditional computational fluid dynamics (CFDs) require as internal training data. The architecture is devised to enforce the initial and boundary conditions, and incorporate the governing equations and the low-resolution spatiotemporal internal data into the loss function of the neural network, to drive the training. Compared to the original PINN with no internal data, the training and predicting dynamics of HCDD-PINN with different resolutions of coarse internal data are analyzed on the problem relevant to the two-dimensional unsteady flapping wing, which involves unsteady flow features and moving boundaries. Additionally, a hyper-parametrical study is conducted to obtain an optimal model for the problem under consideration, which is then utilized for investigating the effects of the snapshot and fraction of the coarse internal data on the HCDD-PINN’s performances. The results show that the proposed framework has a sufficient stability and accuracy for solving the considered biomimetic flapping-wing problem, and its great potential means that it can be considered as an alternative to accelerate or replace traditional CFD solvers in the future. The interested variables of the flow field at any instant can be rapidly obtained by the trained HCDD-PINN model, which is superior to the traditional CFD method that usually needs to be re-run. For the three-dimensional and optimization problems of flapping wings, the advantages of the proposed method are supposedly even more apparent. Full article
(This article belongs to the Special Issue New Insights into Biological and Bioinspired Fluid Dynamics)
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11 pages, 4182 KiB  
Article
Interfacial Dynamics in Dual Channels: Inspired by Cuttlebone
by Matthew Huang, Karl Frohlich, Ehsan Esmaili, Ting Yang, Ling Li and Sunghwan Jung
Biomimetics 2023, 8(6), 466; https://doi.org/10.3390/biomimetics8060466 - 1 Oct 2023
Viewed by 1092
Abstract
The cuttlebone, a chambered gas-filled structure found in cuttlefish, serves a crucial role in buoyancy control for the animal. This study investigates the motion of liquid-gas interfaces within cuttlebone-inspired artificial channels. The cuttlebone’s unique microstructure, characterized by chambers divided by vertical pillars, exhibits [...] Read more.
The cuttlebone, a chambered gas-filled structure found in cuttlefish, serves a crucial role in buoyancy control for the animal. This study investigates the motion of liquid-gas interfaces within cuttlebone-inspired artificial channels. The cuttlebone’s unique microstructure, characterized by chambers divided by vertical pillars, exhibits interesting fluid dynamics at small scales while pumping water in and out. Various channels were fabricated with distinct geometries, mimicking cuttlebone features, and subjected to different pressure drops. The behavior of the liquid-gas interface was explored, revealing that channels with pronounced waviness facilitated more non-uniform air-water interfaces. Here, Lyapunov exponents were employed to characterize interface separation, and they indicated more differential motions with increased pressure drops. Channels with greater waviness and amplitude exhibited higher Lyapunov exponents, while straighter channels exhibited slower separation. This is potentially aligned with cuttlefish’s natural adaptation to efficient water transport near the membrane, where more straight channels are observed in real cuttlebone. Full article
(This article belongs to the Special Issue New Insights into Biological and Bioinspired Fluid Dynamics)
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13 pages, 5028 KiB  
Article
Bio-Inspired Aquatic Propulsion Mechanism Using Viscoelastic Fin Containing Fiber Composite Shear Thickening Fluid
by Shunichi Kobayashi and Kousuke Sugiyama
Biomimetics 2023, 8(5), 405; https://doi.org/10.3390/biomimetics8050405 - 1 Sep 2023
Viewed by 960
Abstract
Many propulsion mechanisms utilizing elastic fins inspired by the caudal fins of aquatic animals have been developed. However, these elastic fins possess a characteristic whereby the rigidity required to achieve propulsion force and speed increases as the oscillation velocity increases. Therefore, by adding [...] Read more.
Many propulsion mechanisms utilizing elastic fins inspired by the caudal fins of aquatic animals have been developed. However, these elastic fins possess a characteristic whereby the rigidity required to achieve propulsion force and speed increases as the oscillation velocity increases. Therefore, by adding an actuator including a variable stiffness mechanism to the fin it is possible to maintain the optimal stiffness at all times. However, if the aforementioned characteristics allowing the fin itself to change stiffness are present, the need for a variable stiffness mechanism is eliminated, leading to possibilities such as the simplification of the mechanism, improvements in fault tolerance, and enhancements in fin efficiency. The authors developed a fiber composite viscoelastic fin by adding fibers to a shear thickening fluid (STF) and examined the speed dependency of the fin’s rigidity. In this work, we examined the structure and speed dependency of the fin’s rigidity, as well as the propulsion characteristics in still water and in uniform flow. As a result, the fiber-containing fin containing the STF oobleck (an aqueous suspension of potato starch) demonstrated higher propulsion in still water and higher self-propelled equivalent speed in uniform water flow than elastic fins. Full article
(This article belongs to the Special Issue New Insights into Biological and Bioinspired Fluid Dynamics)
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15 pages, 1647 KiB  
Article
How Free Swimming Fosters the Locomotion of a Purely Oscillating Fish-like Body
by Damiano Paniccia, Luca Padovani, Giorgio Graziani, Claudio Lugni and Renzo Piva
Biomimetics 2023, 8(5), 401; https://doi.org/10.3390/biomimetics8050401 - 1 Sep 2023
Viewed by 1087
Abstract
The recoil motions in free swimming, given by lateral and angular rigid motions due to the interaction with the surrounding water, are of great importance for a correct evaluation of both the forward locomotion speed and efficiency of a fish-like body. Their contribution [...] Read more.
The recoil motions in free swimming, given by lateral and angular rigid motions due to the interaction with the surrounding water, are of great importance for a correct evaluation of both the forward locomotion speed and efficiency of a fish-like body. Their contribution is essential for calculating the actual movements of the body rear end whose prominent influence on the generation of the proper body deformation was established a long time ago. In particular, the recoil motions are found here to promote a dramatic improvement of the performance when damaged fishes, namely for a partial functionality of the tail or even for its complete loss, are considered. In fact, the body deformation, which turns out to become oscillating and symmetric in the extreme case, is shown to recover in the water frame a kind of undulation leading to a certain locomotion speed though at the expense of a large energy consumption. There has been a deep interest in the subject since the infancy of swimming studies, and a revival has recently arisen for biomimetic applications to robotic fish-like bodies. We intend here to apply a theoretical impulse model to the oscillating fish in free swimming as a suitable test case to strengthen our belief in the beneficial effects of the recoil motions. At the same time, we intend to exploit the linearity of the model to detect from the numerical simulations the intrinsic physical reasons related to added mass and vorticity release behind the experimental observations. Full article
(This article belongs to the Special Issue New Insights into Biological and Bioinspired Fluid Dynamics)
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23 pages, 8417 KiB  
Article
Computational Study of Stiffness-Tuning Strategies in Anguilliform Fish
by Zuo Cui and Xuyao Zhang
Biomimetics 2023, 8(2), 263; https://doi.org/10.3390/biomimetics8020263 - 16 Jun 2023
Cited by 1 | Viewed by 1247
Abstract
Biological evidence demonstrates that fish can tune their body stiffness to improve thrust and efficiency during swimming locomotion. However, the stiffness-tuning strategies that maximize swimming speed or efficiency are still unclear. In the present study, a musculo-skeletal model of anguilliform fish is developed [...] Read more.
Biological evidence demonstrates that fish can tune their body stiffness to improve thrust and efficiency during swimming locomotion. However, the stiffness-tuning strategies that maximize swimming speed or efficiency are still unclear. In the present study, a musculo-skeletal model of anguilliform fish is developed to study the properties of variable stiffness, in which the planar serial-parallel mechanism is used to model the body structure. The calcium ion model is adopted to simulate muscular activities and generate muscle force. Further, the relations among the forward speed, the swimming efficiency, and Young’s modulus of the fish body are investigated. The results show that for certain body stiffness, the swimming speed and efficiency are increased with the tail-beat frequency until reaching the maximum value and then decreased. The peak speed and efficiency are also increased with the amplitude of muscle actuation. Anguilliform fish tend to vary their body stiffness to improve the swimming speed and efficiency at a high tail-beat frequency or small amplitude of muscle actuation. Furthermore, the midline motions of anguilliform fish are analyzed by the complex orthogonal decomposition (COD) method, and the discussions of fish motions associated with the variable body stiffness and the tail-beat frequency are also presented. Overall, the optimal swimming performance of anguilliform fish benefits from the matching relationships among the muscle actuation, the body stiffness, and the tail-beat frequency. Full article
(This article belongs to the Special Issue New Insights into Biological and Bioinspired Fluid Dynamics)
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