3D velocity fields for the Burger vortex flow treatments

A laboratory apparatus was constructed to physically create a Burgers vortex. Fluid motion is induced by co-rotating two disks while simultaneously withdrawing fluid axially through hollow drive shafts. The technique creates a flow pattern that mimics a Burgers vortex with size and strength consistent with dissipative-scale turbulent eddies in the coastal and near-surface zones. Specifically, the radius, circulation, and axial strain rate of the Burgers vortex were specified to match typical dissipative vortices corresponding to four turbulence intensity levels (described by a mean turbulent dissipation rate of 0.002, 0.009, 0.096, and 0.25 cm2s-3, respectively).

Tomographic particle image velocimetry (tomo-PIV) was used to quantify the flow field, calibrate the apparatus, verify that it produces the desired vortex characteristics, and provide a three-dimensional velocity vector field to compare with zooplankton behavioral assays. The apparatus facilitates direct examination of the mechanistic aspects of plankton interaction with a dissipative-scale turbulent eddy. In depth description of the laboratory setting can be found at Webster and Young, 2015, and Elmi et al., 2021.