Improved ADCP Performance Using a Hydrodynamically Designed Boom Mount

Abstract

This paper presents the results of the design and testing of a hydrodynamic mount for a direct-reading 150-kHz acoustic Doppler current profiler (ADCP) operated over the side of a small inshore vessel in transect mode (i.e., while steaming). The mount consists of a symmetric wing section encompassing the ADCP pressure housing and a custom teardrop-shaped fairing surrounding the transducer heads. It was found that the longitudinal (along-ship) force resulting from the form drag and the wave generation on the hydrodynamic mount was less than one-half of that on the unfaired ADCP. This together with improved flow characteristics resulted in a reduction in the standard deviations of the measured currents from 6 to 10 em s?1 during a survey in 1990 without the fairing to 3?5 cm s?1 for a survey in 1991 with the fairing. The mount also permitted a doubling in ship speed from about 2.0 to 4.0 m s?1 (4?8 kt). The results also indicate the minimum noise levels that can be expected at the spatial resolutions usually required in inshore regions.