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Spatiotemporal Asymmetry in Metachronal Rowing at Intermediate Reynolds Numbers
Adrian Herrera-Amaya1, Elizabeth K Seber1, David W Murphy2
1Department of Mechanical Engineering, Penn State University, University Park, PA, 16802, USA.
Integrative and Comparative Biology
|August 19, 2021
Summary
Organisms use spatial and temporal asymmetry for propulsion at low Reynolds numbers. This study reveals how both asymmetries contribute to force generation in metachronal rowing, with implications for understanding biological locomotion.
Area of Science:
- Fluid Dynamics
- Biomechanics
- Animal Locomotion
Background:
- Drag-based swimming at low Reynolds numbers requires spatially asymmetric strokes for net fluid displacement.
- Metachronal rowing, common in nature, involves sequential appendage movement and becomes more complex as inertia increases.
- The interplay between spatial and temporal asymmetry in metachronal rowing is not fully understood.
Purpose of the Study:
- To investigate the combined effects of spatial and temporal asymmetry on thrust generation in metachronal rowing.
- To explore how body size and Reynolds number influence these asymmetries in lobate ctenophores.
- To develop a model predicting propulsive forces based on kinematic parameters and Reynolds number.
Main Methods:
- Laboratory experiments measuring beat kinematics and fluid flow in ctenophores of varying sizes (7-40 mm).
- Reduced-order analytical modeling using a one-dimensional system of oscillating plates.
- Analysis of flow patterns and force generation across a range of Reynolds numbers and kinematic parameters.
Main Results:
- Observed distinct flow patterns in ctenophores related to body size and Reynolds number.
- Found a trend of decreasing spatial asymmetry and increasing temporal asymmetry with rising Reynolds number.
- Model results indicate both asymmetries enhance force production, with differing impacts across parameter spaces.
Conclusions:
- Spatiotemporal asymmetry plays a crucial role in metachronal rowing across different Reynolds numbers.
- Temporal asymmetry offers a potentially controllable mechanism for thrust enhancement, unlike passive spatial asymmetry.
- Findings provide insights into the evolution and mechanics of biological propulsion.
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