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.