An Evaluation of Several Techniques for Reducing Cable Strum.

摘要

The usefulness of various appendages in reducing towcable strum was experimentally investigated for a towcable inclined at fifteen degrees to the oncoming flow. This angle was chosen as being representative of angles occurring in sonar array towing where strumming is believed to be a significant contributor to low frequency self-noise in the array. The measure of the efficacy of the strum reduction is based on the relative levels of the transverse acceleration at the center of a taut cable with and without the strum reducing appendages. The cable was 0.53 inches (135 mm) in diameter and was 18.5 feet (5.6 m) long. Under the experimental conditions, certain types of appendages were found to be almost useless. The more useful ones were helical wire wrap, ribbon fairing and a commerical strip fairing. All of these appendages cause a higher value of tangential drag than does bare cable, and a comparison of these drag values is made. As a result of the experiment a new method of strum reduction, called stub fairing, was found to have good strum reduction efficiency but with much less drag penalty than the ribbon and the commercial fairing. (Author)