Time resolved measurements of the flow generated by suction feeding fish |
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Authors: | Steven W Day Timothy E Higham Peter C Wainwright |
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Institution: | (1) Department of Mechanical Engineering, Rochester Institute of Technology, 76 Lomb Memorial Dr, Rochester, NY 14623, USA;(2) Department of Organismic and Evolutionary Biology, Concord Field Station, Harvard University, 100 Old Causeway Road, Bedford, MA 01730, USA;(3) Section of Evolution and Ecology, University of California, One Shields Avenue, Davis, CA 95616, USA |
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Abstract: | The majority of aquatic vertebrates are suction feeders: by rapidly expanding the mouth cavity they generate a fluid flow
outside of their head in order to draw prey into their mouth. In addition to the biological relevance, the generated flow
field is interesting fluid mechanically as it incorporates high velocities, is localized in front of the mouth, and is unsteady,
typically lasting between 10 and 50 ms. Using manometry and high-speed particle image velocimetry, this is the first study
to quantify pressure within and outside the mouth of a feeding fish while simultaneously measuring the velocity field outside
the mouth. Measurements with a high temporal (2 ms) and spatial (<1 mm) resolution were made for several feeding events of
a single largemouth bass (Micropterus salmoides). General properties of the flow were evaluated, including the transient velocity field, its relationship to pressure within
the mouth and pressure at the prey. We find that throughout the feeding event a relationship exists for the magnitude of fluid
speed as a function of distance from the predator mouth that is based on scaling the velocity field according to the size
of the mouth opening and the magnitude of fluid speed at the mouth. The velocity field is concentrated within an area extending
approximately one mouth diameter from the fish and the generated pressure field is even more local to the mouth aperture.
Although peak suction pressures measured inside the mouth were slightly larger than those that were predicted using the equations
of motion, we find that these equations give a very accurate prediction of the timing of peak pressure, so long as the unsteady
nature of the flow is included. |
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