Tunas with Laser Beams!
A yellowfin tuna swims in the flume as an
infrared laser beam reveals the flow patterns around its tail (photo B. Block)
A collaborative project between
Massachusetts Institute of Technology and the TRCC team has been undertaken to
characterize the water flow around live, swimming tunas. Professor Block and visiting MIT Professor
Alexandra Techet and graduate student Leah Mendelson have been leading the charge
on this complex and challenging study. The
team is on a mission to better understand the underlying mechanisms that enable
these highly streamlined organisms to swim at high speed and migrate across
ocean basins.
MIT graduate student Leah Mendelson dawns
her laser safety glasses as she captures high speed footage of the swimming
tuna (photo B. Block)
Over the past 6 months Postdocs Adrian
Gleiss and Jon Dale and graduate student Dane Klinger have trained bluefin and yellowfin
tuna to swim steadily in the lab’s respirometer. This specialized tank generates flow that
enables the tuna to swim in place in a sealed acrylic chamber. The tunas become acclimated to swimming in
the environment through subsequent runs in the respirometer, and for this
week’s project we’ve selected the calmest, most steady-swimming individuals as
brave test pilots for this never-before-attempted study.
High-speed footage of the illuminated
particles, seen here flowing over a bluefin tuna’s finlets, will be input into
a mathematical model that will reconstruct the fluid motion around these
features (video B. Block)
The
team is applying a technique called PIV (Particle Imaging Velocimetry) to
observe the fluid flow around the body and fins of a swimming tuna. This technique involves seeding the seawater
in the respirometer with small (20 micron) polyamide particles, which when
illuminated by an infrared laser beam enable a high-speed camera to track the
motion of each individual particle.
Subsequent analysis of this high-speed footage will enable the
researchers to construct mathematical models of the particle movement around
various features of the fish. For the
first time, we will be able to visualize the fluid flow from the head to tail
of a swimming tuna. Stay tuned to check
out the results of this cutting edge project.
(left-to-right) Graduate student Leah Mendelson, Professor Alexandra Techet, and Professor Barbara Block in front of the TRCC at Hopkins Marine Station (photo E. Estess)
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