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Enhancing propulsion performance of a flexible heaving foil through dynamically adjusting its flexibility
Chenglei Wang1, Feng Ren, Hui Tang
1Research Center for Fluid-Structure Interactions, Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, People's Republic of China.
Bioinspiration & Biomimetics
|September 19, 2019
Summary
Dynamically adjusting a heaving foil's bending stiffness can enhance propulsion thrust at low Reynolds numbers. Optimal performance occurs with moderate stiffness bounds and specific timing during oscillation cycles.
Area of Science:
- Fluid-Structure Interaction (FSI)
- Bio-inspired Propulsion
- Computational Fluid Dynamics (CFD)
Background:
- Understanding fluid dynamics and structural responses is crucial for designing efficient aquatic vehicles.
- Previous studies often assume constant material properties, limiting the exploration of dynamic control strategies.
- Heaving foils are a common model for studying underwater locomotion.
Purpose of the Study:
- To investigate the impact of dynamically adjusting bending stiffness on the propulsive performance of a heaving foil.
- To explore the relationship between stiffness tuning parameters (bounds, duty cycle, phase angle) and net thrust/efficiency.
- To analyze the interplay of various forces governing the foil's dynamics under time-varying stiffness.
Main Methods:
- Numerical simulation using an immersed boundary lattice Boltzmann method (IBLBM).
- Modeling a heaving foil with sinusoidally forced oscillation at the leading edge.
- Implementing square-wave tuning of the foil's bending stiffness.
Main Results:
- Moderate, dynamically adjusted bending stiffness significantly enhances net thrust compared to constant stiffness.
- Propulsion efficiency shows limited improvement with dynamic stiffness adjustment.
- Optimal thrust enhancement is achieved with a 1/2 duty cycle and stiffness held at the lower bound during stroke reversals.
Conclusions:
- Dynamic tuning of bending stiffness is a viable strategy for improving heaving foil thrust generation.
- Careful selection of stiffness bounds and timing is critical for maximizing propulsive performance.
- The study elucidates the complex force dynamics influencing foil motion under variable stiffness conditions.
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