Maneuverability towing tank experiments with manifold models: part II - PMM oscillation tests

This work is the Part II of a two-part work, where the influence of geometrical simplifications and modifications in the maneuverability of a manifold were investigated by three 1:13 scaled models in a towing tank. In this work is presented the adopted methods that were used to obtain the hydrodynamic derivatives from forced oscillations motions in a towing tank using a planar-motion-mechanism. In the part I was presented the static drift tests, which were used to complement the tests presented in this paper. The maneuvering hydrodynamic derivatives are obtained by a two part analysis. First, the measured forces, moments and motions time series signals are filtered and decomposed in harmonic functions. Second, regression analysis techniques are applied to the amplitude of these harmonic functions in order to estimate the hydrodynamic derivatives. The results have showed that the simplification of the manifold geometry has a low influence in the hydrodynamic derivatives in contrast to the installation of a larger plate, which modified the manifold maneuverability significantly. The presented investigation in both papers will be used to form a data base for numerical simulation studies for manifolds installation.