SuperBASS tripod for benthic turbulence measurement

Abstract

Seafloor flow induced processes are generally studied from rigid structures. Where undisturbed flow is important, open structures are used, tripods being the choice for omnidirectional flow. Stiffness as well as openness is important to delay excitation of vibrations that can contaminate velocity measurements, masking turbulence in the flow. SuperBASS, measuring velocity and turbulence at seven heights from 0.3 to 7 m above bottom, is 8 m tall, 4 m between footpads, weighs 530 kg, and is stable to overturning to 1 m/s flow velocity. A "Y" channel of rectangular cross section from the bottom of the legs supports the base of the acoustic current meter array, eliminating the need for stiffener struts on the faces of the tripod. While this design reduces turbulence at all sensor heights that would have come from the wake of upstream stiffening struts, a mean upward component of flow is observed on the lower sensors from separation of the flow over the "Y" channel near the seabed.