Intake flow fields for a zooplankton pump sampling system

Abstract

The flow fields entering intake forms oriented into a steady flume flow has been observed and quantified. This data is applied to a model of zooplankton sampler performance, to predict the fraction of the sampled fluid from which no animals will escape under conditions similar to those of the tests. Flume flow speeds (≈5 cm/s) and intake pumping rate (≈33 gal/min) are scaled by a factor of 20 in the model, while test form dimensions (4 and 7 inch throats and 12 inch outside diameters) are considered to be full-size for the prototype pump samplers. The data presented can be applied to other flow and geometrical scales. The 'lethal cone' and critical fluid deformation rate envelopes are evaluated for eleven intake forms: pointed, bullet-shaped, funnel-shaped, rounded and square-ended. The sharply-pointed intake performed test, for tow speed ≈100 cm/s, swimming speed=30 cm/s and Dc=1. 0 sec-1. 'Sure capture' is predicted in 83% of the sampled water. The four funnel-shaped forms follow consecutively in a rank ordering, with efficiencies, of 77% to 68%.