OCEAN CURRENT PREDICTION IN TOWED CABLE HYDRODYNAMICS UNDER DYNAMIC STEERING

This paper considers the problem of reconstructing the velocities of o cean currents impinging on a towed streamer cable sparsely equipped with steerin g elements. The study is based on a two-dimensional model describing the quasi-s teady motion of the towed cable in the presence of hydrodynamic drag and steerin g forces that depend nonlinearly on the angle of attack. To derive the proposed methodology we firstly outline the hydrodynamic equations used in solving the for ward problem by which the cable’s velocity, curvature and tension are obtained i n the knowledge of the towing vessel’s motion, the ocean current velocities and the drag coefficient characteristics of the steering elements. In sequence we form ulate the inverse problem of inferring the ocean velocities using a finite set of noise-infused positioning and tension measurements showing that this is nonline ar and ill-posed. To solve the inverse problem we adopt Newton’s scheme for nonl inear convex problems in conjunction with generalized Tikhonov regularization. T he problem under consideration bares significant differences from the linear non-s teered formulation addressed in (12), due to the nonlinearity in the forward met hod as well as the discontinuities observed in the forward measurements due to t he steering forces. A series of numerical simulation studies is subsequently pre sented in order to demonstrate the practical performance of the proposed techniq ue in reconstructing the ocean currents velocity profile and angle of attack