We look at a variety of fluid dynamics at low or intermediate Reynolds numbers, including the rising of oil droplets and feeding and swimming of marine invertebrates.
Feeding and Swimming of Marine Invertebrates
Many marine invertebrates have a swimming larval stage, such as sea urchins and tunicates (sea squirts). We use high-speed videography to quantify and study these currents.
Suspension feeding and swimming currents produced by Arbacia punctulata larva:
Slowed detail of cilia producing currents:
Close-up detail of end of larval arm and individual cilia:
Tunicate larvae are very small tadpoles with tails and swim in a way similar to fish:
Current work involves quantifying flow fields around these creatures and others.
Oil Droplets Rising Through Sharp Stratifications
In a postdoc with Dr. Shilpa Khatri (Univ. of California, Merced), the motion and interactions of small oil droplets (~ 1-3 mm in diameter) traveling through a sharply stratified water layer were investigated with high-speed videography.
Sharp stratifications occur in the ocean between layers of water with very different densities (due to temperature or salinity). Oil droplets are slowed down through this transition, because they drag heavier, bottom-layer fluid up through lighter, top-layer fluid, making a beautiful contrast to visualize forming vortices and droplet interactions.
Single droplet traveling in top-layer water (pure water) with highlights due to high-salinity, bottom-layer water:
Two droplets interacting in a draft-kiss-tumble maneuver:
These visualizations will be compared to a computational model of oil-droplet motion through stratifications.
Waldrop Lab 