Professor, Vanderbilt University
1. How did you first get involved with SEN?
Siobhan Fathel first convinced me to pay attention to SEN, based on her conversations with Raleigh Martin regarding the objectives of SEN and the significance of archiving experimental data in a manner that makes the data readily available to other researchers. Indeed, Siobhan’s data based on high-speed imaging of bed load sediment motions are available on the SEN website, and they have been used by others.
2. What different types of experiments have you worked with?
- Visualization and measurement of the deformation and response of artificial tree roots during soil shear
- The development of flow instabilities (flow fingering) during water infiltration into soils
- Visualization and flow velocity measurements of fluid circulation within an experimental tidally driven Hele-Shaw cell
- High-speed imaging and analysis of particle motions and transport due to rain drop impacts
- High-speed imaging and analysis of bed load particle motions and transport within a turbulent shear flow
- Measurements of particle ravel and travel distances on the surface of a large laboratory-scale “hillslope”
3. What is a favorite memory of yours in the lab?
Holy Moly this is not a fair question! I have no favorite memory of being in the lab! I have a gazillion memories of delightful stuff happening in a lab! OK... so you need highlights. Here are some...
To do the Hele-Shaw experiments we mixed zinc-coated micro-balloon tracer particles within glycerin, and projected a laser sheet upward into the narrow Hele-Shaw cell. The laser illuminated the tracer particles. The lab had to be entirely dark to do the high-speed and time-lapse imaging. The first time we turned off the lights and saw the tracer particles doing their lovely dances in the cell was, like, wow! We referred to their sparkly light show as Starry Starry Night!
Our first set of experiments dropping water drops on sand targets typically involved dropping many tens of drops before one landed precisely on the target. This meant that, for the many not-quite-right drop impacts, we had to reconfigure the target and reset the highspeed imaging system. When we finally got to watch the replay of the first successful impact, and saw in the slow motion the amazing fluid-particle and particle-particle interactions during impact together with the arched trajectories of the splashed particles — all occurring within less than one tenth of one second in real time — well, we were all quite amazed and delighted!
During our recent experiments involving high-speed imaging of bed load particles, I was the “official” photographer of activities and events. This really meant that I got to watch Kate Potter Leary, Siobhan Fathel and Mark Schmeeckle do their carefully choreographed tasks of preparing the flume sediment, setting up the dual cameras and high-intensity strobe lighting, adjusting the laser sheet (that was my task), setting the flow, acquiring the images, and taking flow velocity measurements. All steps had to be just right. So one can imagine that the several-days effort was an important lesson in patience. And by the end of the experiments, we were really good at it! (Oh... and we all got to wear cool protect-or-eyesfrom-the-laser goggles! They made us look like real scientists. :-)
4. What do you hope SEN will help the experimental community to achieve?
I would hope SEN activities open opportunities to grow community interest in developing and using novel and perhaps unusual experimental approaches and techniques, and methods of data processing and analysis... things we have not yet seen or thought about. This could also include instrumentation that currently is beyond the budget of an individual investigator, but manageable with a group of investigators pursuing shared ideas. (For example, I sure would like to have the opportunity to play with an ultra high frame-rate camera without loss of resolution in order to examine certain aspects of sediment particle motions.)