Comparison of drag forces acting on different benthic body shapes in marine molluscs
Abstract
The marine intertidal is an area prone to high wave energy and flow velocities,
and the organisms living there are subjected to large hydrodynamic forces, such as drag.
These forces acting to dislodge organisms may result in reduced foraging efficiency and
depressed overall growth. In this study the body shape of a snail, chiton, and limpet are
subjected to flume testing to observe how drag forces and drag coefficients change with a
range of Reynolds numbers simulating currents up to 6 m/s. In higher flow velocities the
snail body shape experienced drastically higher drag forces than the limpet and chiton
body shape. The drag coefficients for the limpet and chiton both were relatively high at
low flow velocity, and quickly decreased at higher speeds. The snail however
experienced an opposite change in drag coefficient, with a lower drag coefficient at low
flow speeds and increased with higher flow speeds. When compared to Reynolds number
drag coefficients for the limpet and chiton show little change at higher Reynolds number,
contrast to the snail body shape in which the drag coefficient appears to fluctuate with
increasing Reynolds number.