Inverse problem in determining the normal and tangential drag coefficients of marine cables

The Levenberg-Marquardt method is applied to estimate simultaneously the normal and tangential drag coefficients of marine cable, in a planarly towed cable-body system, from the measurements of the horizontal and vertical tension force components. Because only coefficients are to be estimated, this type of problem belongs to a branch of systems identification called `parameters estimation'. A statistical analysis is performed to determine the standard deviation and the approximate confidence bounds for estimating the normal and tangential drag coefficients. Results show that the sensitivity and accuracy of the estimated coefficients depend on the type of boundary conditions used in the direct problem as well as on the towed configurations.