Acoustic Doppler Velocimeter Evaluation in Stratified Towing Tank

The performance of an acoustic Doppler velocimeter (ADV) was evaluated using a towing tank. Rudimentary tests of the speed response were followed by tests of yaw and pitch response. Because only a few published (and inconsistent) values of sound speed as a function of saltwater concentration were found, a simple scheme was devised using the boundary-detection feature of the ADV to obtain such values. Tests were also run in the stratified tank to verify the usability of the ADV there. The accuracy of the probe to horizontal flow fields is generally within the range of ±0.25% ± 0.25 cm/s, and the yaw response is very nearly sinusoidal. Limited pitch-response tests suggested an indicated overspeed of some 5–10% for horizontal velocities and an indicated underspeed of 5–15% for vertical velocities. A correction scheme was developed to allow the ADV to be used in high-concentration saltwater, and its suitability was verified in homogeneous saltwater solutions. When the same scheme was used in a strongly stratified tank, however, a small overcorrection was indicated. Tests on a new probe design suggested much improved pitch response.