State-of-the-art Experimental Fluid Mechanics Towards Resolving Biophysical Processes in Marine Ecosystems


In the last few decades, a fascinating and interdisciplinary world of research has exploded which examines the coupling of biological, chemical, and physical realities in marine ecosystems. From chemotactic bacterial tracking of free-falling marine snow aggregates to turbulent “unmixing” of motile phytoplankton, this fruitful field promises to yield big answers to big questions. Here, we present design work, numerical modeling, and preliminary experimental findings related to two biophysically-inspired projects as illustrative examples of how we are leveraging state-of-the-art methods from experimental fluid mechanics to investigate fundamental and far-reaching problems in marine ecosystems: siphon-generated flows from benthic bivalves and the dynamics of motile phytoplankton in turbulent flows. For the siphon-flow project, numerical modeling (COMSOL) not only revealed nontrivial departures from the idealized inviscid flow fields at low Reynolds number but also gave critical insights used to design an index of refraction-matched flume facility in which we will employ planar particle image velocimetry (PIV) to quantify transient and steady state flow fields both within and outside the siphon tube. For the phytoplankton-turbulence project, we’ve built a 1 L oscillating grid turbulence tank, quantified the turbulence characteristics via PIV, and directly imaged distributions of a motile dinoflagellate (Heterosigma akashiwo) in nearly homogeneous, isotropic turbulence via planar laser-induced fluorescence (PLIF) of the cells themselves. Preliminary spatial probability distribution functions revealed patches of cells with concentration enhancement factors comparable to those found in a direct numerical simulation (DNS) of motile “cells” in turbulence. As these projects are very much in their infancy, we freely invite questions, critiques, and suggestions to sharpen and hone the science!

Mar 10, 2015 3:30 PM — 4:30 PM
Bechtel Collaboratory, Discovery Learning Center
Engineering Center, University of Colorado at Boulder, Boulder, CO 80309

University of Colorado Boulder