Hydroacoustic measurements of velocities in and near the rake-to-box junction gap of a moving, fully-loaded commercial barge tow

In August 2015, water velocities around a fully-loaded commercial barge tow were measured as the barge tow traveled upstream through the Chicago Sanitary and Ship Canal from a starting position in Lockport Pool, and passed through the Electric Dispersal Barrier System at RM 296 near Romeoville, IL. Velocity measurements were made in and alongside the gap formed by the junction between the boxed stern of a rake hopper barge and the raked bow of a rake tanker barge (herein referred to as the rake-to-box junction gap) using two SonTek Argonaut SW 3kHz acoustic Doppler velocity meters (ADVM).
One ADVM was mounted 0.091 meters below the water surface, facing downward in the center of the rake-to-box junction gap, rotated 35 degrees clockwise to the box side of the gap (Downlooking ADVM). The other ADVM was mounted 1.37 meters below the water surface at the edge of the rake-to-box junction gap, facing outward from the barge tow at an angle of 23 degrees measured counter-clockwise from a line perpendicular to the barge (Side-looking ADVM). Differential GPS (dGPS) receivers were mounted directly above both ADVMs and their output was logged in HYPACK (more information available at http://www.hypack.com). The dGPS mounted above the Downlooking ADVM also logged GPS Doppler-based heading information with an accuracy of ± 0.75°.
The water velocity data are reported in a stationary, course-oriented reference frame (i.e. corrected for the movement of the barge tow), such that positive course-parallel velocities point in the direction of barge travel (upstream, for this dataset), and positive course-normal velocities point into the gap (toward the right, when facing in the direction of barge travel). Profiles of mean course-parallel velocity and mean course-normal velocity are reported for several ranges of barge tow speed. The distance from the barge (Side-looking ADVM) and the distance below the water surface (Downlooking ADVM) are given for the center of each ADVM measurement cell.