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Hydrodynamic evaluation of a spider-inspired underwater robot using distributed flapping fin propulsion
Vishnu G Nair1, Rithvik Marneni1, B Gowrava Shenoy1
1Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, India.
Scientific Reports
|June 13, 2026
Summary
This study introduces a spider-inspired hexapod robot with distributed flapping fins for efficient underwater propulsion. This novel design offers enhanced maneuverability and energy efficiency for marine exploration.
Area of Science:
- Robotics and Mechanical Engineering
- Fluid Dynamics
- Bio-inspired Design
Background:
- Conventional underwater robots often rely on centralized fin actuation, limiting maneuverability and stability.
- Bio-inspired designs offer potential for improved performance, but require rigorous hydrodynamic evaluation.
- Developing energy-efficient and stable underwater robotic platforms is crucial for marine tasks.
Purpose of the Study:
- To design and hydrodynamically evaluate a spider-inspired underwater hexapod robot with distributed flapping-fin propulsion.
- To investigate the lift generation, drag, and stability characteristics of the novel propulsion system.
- To establish the hydrodynamic feasibility and energetic advantages of this bio-inspired approach.
Main Methods:
- Quasi-steady analytical estimations of lift, drag, and lift-to-power scaling.
- Transient Computational Fluid Dynamics (CFD) simulations using ANSYS Fluent.
- Preliminary experimental validation with a laboratory-scale prototype.
Main Results:
- Close agreement between theoretical, numerical, and experimental results (lift predictions within ±10-15%).
- Stable hydrodynamic performance observed at fin-tip velocities of 0.6-0.8 m/s.
- A consistent lift-to-drag ratio of approximately 1.3 and efficient Strouhal number operation confirmed.
Conclusions:
- The distributed flapping-fin propulsion system integrated with a multi-legged architecture is hydrodynamically feasible.
- The proposed design offers significant energetic advantages over conventional methods.
- Validated insights are provided for developing maneuverable and energy-efficient underwater robots for inspection, monitoring, and exploration.
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