Fish-Inspired Propulsion through a Water-Air Interface

Archer fish are capable of accurately jumping for aerial prey from a stationary aiming position directly below the water’s surface. This jumping behavior may provide a bioinspired strategy for water-exit in underwater vehicles, especially in sensitive environments where other thrusters (e.g., high-pressure water jets) may be too disruptive. However, any engineered implementation of this behavior relies on the ability to simplify, replicate, and optimize archer fish-inspired propulsion using a mechanical system. In particular, flapping flexible plates and hydrofoils are commonly-used simplified mechanical models of fish locomotion. This project aims to use these models to understand why the archer fish changes the timing and size of each tailbeat as it leaves the water and how to optimally execute similar kinematic variations.

We use a combination of experimental and computational models to determine how changing the amplitude and timing of each propulsive “tailbeat” affects cumulative propulsion during water-exit. Is it better to execute faster, smaller-amplitude motions or larger, sweeping ones? How does the optimal motion vary with the size and flexibility of the actuator? Can we time each motion such that a beneficial interaction with the wake of the previous tailbeat is achieved? At what point during water-exit does force production reach diminishing returns, where so little of the plate or foil is underwater that additional “tailbeats” do not significantly contribute thrust?

Experimental efforts to answer these questions include designing and prototyping mechanisms to replicate the kinematics of jumping fish and analyzing the forces and flow patterns produced by these mechanical models using high speed imaging, dye visualization, six axis force sensing, and particle image velocimetry.

Computational efforts to answer these questions combine Computational Fluid Dynamics simulations (using open-source software) and mathematical modeling. In particular, we focus on using simulations to inform experiment design and on modeling the stability of a partially-submerged, flapping-actuated inverted pendulum (think dolphin tailstand).

Research will take place during the Fall and Spring semesters for academic credit. Paid summer students will be recruited from within the research group contingent on funding.

Essay Prompt (~paragraph length): Why are you interested in working on this research project? What will you bring to the project and what do you hope to learn? Please also submit the names of two HMC professors as references who can comment on your work habits.

Name of research group, project, or lab
Flow Imaging Lab at Mudd
Why join this research group or lab?

Students will join a collaborative team working at the interface of biomechanics, fluid mechanics, mechanical design, and computer vision.

The Flow Imaging Lab at (Harvey) Mudd (FILM), directed by Prof. Leah Mendelson, experimentally studies biological and bioinspired fluid mechanics. We mechanically recreate swimming behaviors seen in nature to identify new strategies for underwater vehicle propulsion. The group also works on low-cost tools for flow field measurements. Research projects in FILM frequently involve mechanical design and mechatronics, high-speed imaging, and particle image velocimetry, an experimental technique for measuring fluid velocities by filming the motion of tracer particles suspended in the flow. We frequently use image processing, computer vision, and computational photography to understand the behavior of a fluid flow.

Representative publication
Logistics Information:
Project categories
Fluid Mechanics
Mechanical Engineering
Student ranks applicable
Student qualifications

The following skills and experiences are beneficial but not required:
- Coursework in mechanics, broadly defined (e.g., Phys 24, ENGR 83, ENGR 131)
- Enthusiasm for mechanical design and mechatronics
- Machine shop and makerspace training or willingness to learn
- CAD (Solidworks)
- Programming experience (Matlab, arduino, python, java)
- CS coursework (CS5, CS60, CS70, CS144)

Registration for at least one unit of research credit during the Fall 2022 semester is required.

Time commitment
Fall - Part Time
Spring - Part Time
Academic Credit
Number of openings
Techniques learned

Mechanical Design
Computational Fluid Dynamics
High Speed Imaging
Particle Image Velocimetry
Image Processing

Contact Information:
Leah Mendelson
Name of project director or principal investigator
Leah Mendelson
Email address of project director or principal investigator
2 sp. | 5 appl.
Hours per week
Fall - Part Time (+1)
Fall - Part TimeSpring - Part Time
Project categories
Biomechanics (+4)
EngineeringBiomechanicsFluid MechanicsMechanical EngineeringRobotics