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Abstract Biological systems have often been sources of inspiration for engineering design. Over the past decade, advances in soft robotics have enabled the development of bioinspired technology across a wide range of sizes and applications. When paired with recent advances in miniaturization and manufacturing techniques, soft robotics can be used to investigate the locomotion and bio-hydrodynamics of millimeter-scale swimmers that operate at intermediate Reynolds numbers (100–103). However, it is important to understand the kinematics and dynamics of biological model systems in order to leverage the true potential of bioinspired robots/devices. Ctenophores (comb jellies) are gelatinous marine invertebrates with soft bodies and flexible appendages composed of bundles of millimeter-long cilia; they are the largest animals in the world to locomote using cilia, with each appendage operating at a Reynolds number of approximately 102. Their efficiency, maneuverability, and ubiquity in the global ocean make them a potentially attractive candidate for bioinspired design applications. Each ctenophore has eight rows of paddle-like ciliary bundles (ctenes) that beat metachronally, with a phase lag between neighboring appendages, producing a “metachronal wave” that propagates along the row. This strategy, known as metachronal coordination, is also used by many other organisms (including crustaceans, annelids, and insects) to facilitate feeding, respiration, and locomotion. In general, the performance of a metachronal system depends on a large number of geometrical and dynamical parameters (e.g. beat frequency, phase lag, appendage length, appendage spacing, et al). However, it is unclear how these parameters interact to affect the hydrodynamics of the system overall. We take advantage of natural variation between different species of ctenophores to explore the role of beating frequency, body size, and propulsor spacing in metachronal systems. Using Particle Shadow Velocimetry (PSV), we compare velocity and vorticity fields generated by actively beating ctene rows in three distinct ctenophore species, across a range of beating frequencies and body shapes. Our findings show that ctenophores with more densely packed ctenes (i.e., closer propulsor spacing) generate more coherent flow fields compared to those with higher propulsor spacing at similar Reynolds numbers. Our results highlight the importance of subtle geometric/kinematic differences in driving fluid flow by flexible appendages, and provide a foundation for further investigation of the role of appendage spacing in metachronal coordination for both biological and bioinspired systems.
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Classification of Biological and Bioinspired Aquatic Systems: A Review
Robotic systems capable of aquatic movement has increased exploitation in recent years due to the diverse range of missions that can be performed in otherwise hostile environments. These aquatic unmanned vehicles (AUVs) have begun to transition to systems that replicate biological animals as they are already extremely efficient at moving in aqueous environments. The result is the abandonment of inefficient propeller based locomotion for a biological locomotion type suitable for the specific mission. There is a diverse range of biological locomotion's available with animals that give a range of criteria to follow. In this review, existing aquatic animals and found AUVs are classified. How the bioinspired systems compare to the animals in their locomotion is investigated and discussed. Then, it is discussed what makes these systems bioinspired and biomimetic, and the AUVs that fall into these distinctive categories. Limitations and future recommendations on possible improvements for these systems are offered.
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- Award ID(s):
- 1826758
- PAR ID:
- 10165735
- Date Published:
- Journal Name:
- Ocean engineering
- Volume:
- 148
- ISSN:
- 0029-8018
- Page Range / eLocation ID:
- 75-114
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.oceaneng.2017.11.012
