IBB Breakfast Club Seminar Series
"The Secrets of Swimming in Sand"
Daniel Goldman, PhD - Assistant Professor, School of Physics
I summarize our efforts to understand the locomotion of a sand-swimming lizard, the sandfish, using biological and robotic experiments, and numerical and theoretical models. We use high speed x-ray imaging to study how the 10 cm-long sandfish swims at 2 body-lengths/sec within sand, a granular material that displays solid and fluid-like behavior. Below the surface the lizard no longer uses limbs for propulsion but generates thrust to overcome drag by propagating an undulatory traveling wave down the body. To predict the sandfish swimming speed in the granular ``frictional fluid", we develop an empirical resistive force model by measuring drag force on a small cylinder oriented at different angles relative to the displacement direction and summing these forces over the animal movement profile. The model correctly predicts the animal's wave efficiency (ratio of forward speed to wave speed) as approximately 0.5. The empirical model agrees with a more detailed numerical simulation: a multi-segment model of the sandfish coupled to a multi-particle discrete element method (DEM) simulation of the granular medium. We use the principles discovered to construct a sand-swimming physical model (a robot) which, like in our empirical and multi-particle numerical model, swims fastest using the preferred sandfish wave pattern. The models predict that motor activation force is independent of swimming speed and increases with increasing depth below the surface. Electromyographic (EMG) measurements of epaxial musculature activity in the swimming lizard are in accord with the model predictions.
The IBB Breakfast Club seminar series was started with the spirit of the Institute's interdisciplinary mission in mind. The goal of the seminar series is to highlight research taking place throughout the institute to enable the IBB community to further collaborative opportunities and interdisciplinary research. Faculty are often asked to speak at other universities and conferences, but rarely present at their home institution, this seminar series is an attempt to close that gap. The IBB Breakfast Club is open to anyone in the bio-community. Continental breakfast and coffee will be served.
- Workflow Status: Published
- Created By: Colly Mitchell
- Created: 06/29/2011
- Modified By: Fletcher Moore
- Modified: 10/07/2016