Experimental study on the towing stability of a towed underwater object

The towing stability of a towed underwater object was investigated through towing tank model tests. Three types of towing cables were employed, and the attitude of a towed object was measured by an inertial measurement unit. The towed object's geometry and the position of the towing point were fixed. The lower center of gravity enabled the positive pitch moment due to the increased moment arm and reduced the fluctuation of pitch motion. Three types of appendages, which were vanes, a streamlined bracket, and a spoiler, were employed. The magnitude of the damping force by the vanes and the resulting towing stability depended on the vanes' exposed area to the inflow. The damping force by the streamlined bracket enhanced the pitch stability. On the other hand, the spoiler deteriorated the towing stability as the tilted spoiler resulted in a stall and thereby nonlinear and unfavorable damping force.