Crosstrack Dynamics of a Long Cable Towed in the Ocean

This paper documents a study of the horizontal motion of the downstream end of a towed cable when the motion of the towing vessel is known. The dynamic position of the downstream end of the cable is a consequence of the random crosstrack meandering of the towing vessel as it imperfectly maintains a constant course. The specific purpose of the study was to supply a method to predict the horizontal motion. Other contributors to cable dynamics, such as ocean current, are not addressed. A linear theory for the transverse motion of a cable being towed without purposeful maneuvers was developed. A cable experiment was then performed at sea to verify the linear theory and to establish parameters that would apply operationally in the sea environment. Specifically, the linear transfer function relating the transverse horizontal motion of the upstream and downstream ends of a long steel cable was calculated and measured.