1467. Flume experiments on the hydrodynamics of plankton nets

Experiments on the dynamics of flow into conical plankton nets were conducted at the US Navy's David Taylor Model Basin. A pitot tube and a telemetering flowmeter were used to measure the distribution of flow across the mouths of three 1 m diameter nets with mesh apertures of 0.281 mm, 0.221 mm, and 0.11 1 mm. Velocity profiles at the mouth of bridled nets consistently showed maximum velocity near the margin of the mouth, and a distinct minimum at the centre. The velocity was uniform across the mouth of an unbridled net that was tested. The filtration efficiency of all nets was high at normal towing speeds and remained high up to speeds of 257 cm/sec. Sustained high efficiencies were due in part to stretching of the nylon material from which the nets were constructed