A Procedure for Evaluation, Assessment, and Improvement of Added Mass and Radiation Damping of Floating Structures

Abstract

Currently, the linear diffraction-radiation wave theory is still most-widely used by naval architects and ocean engineers to obtain wave loads on floating structures. The hydrodynamic coefficients (added mass and radiation damping coefficients, wave excitation force transfer functions, second-order wave force functions, etc.) depend only on the shape of the underwater portion of the hull, the wave direction and frequency, and the motion modes. They only need to be evaluated once and stored as a database which can be repeatedly used to calculate the wave loads in different environmental conditions. It is therefore very important to ensure a high quality of the database covering the whole range of wave frequency. This paper presents a practical procedure for the evaluation, assessment and improvement of the added mass and radiation damping coefficients. An accurate semi-analytical method is introduced for the evaluation of the retardation functions and time domain added mass. The quality of the added mass and damping is then assessed using Kramer-Kronig relations. Finally, an iterative method is presented for improving (re-constructing) the added mass and radiation damping so that Kramer-Kronig relations are better satisfied.