INVERSE PROBLEM IN DETERMINING THE NORMAL AND TANGENTIAL DRAG COEFFICIENTS OF MARINE CABLES

The Levenberg-Marquardt method is applied to estimate simultaneously t he normal and tangential drag coefficients of marine cable, in a plana rly towed cable-body system, from the measurements of the horizontal a nd vertical tension force components. Because only coefficients are to be estimated, this type of problem belongs to a branch of systems ide ntification called ''parameters estimation'' (Beck & Blackwell 1988). A statistical analysis is performed to determine the standard deviatio n and the approximate confidence bounds for estimating the normal and tangential drag coefficients. Results show that the sensitivity and ac curacy of the estimated coefficients depend on the type of boundary co nditions used in the direct problem as well as on the towed configurat ions.