Dynamic Oblique Towing Test (DOTT) to calculate the ship's hull maneuvering derivatives

Abstract

An accurate and time-efficient numerical method is developed to find the hydrodynamic maneuvering derivatives with only a single simulation by computational fluid dynamics. The method is based on the oblique towing test by introducing an oscillatory variation to the model ship drift angle as time progress. The fluid flow velocity and direction are fixed during the simulation but the orientation of the model ship is changing sinusoidally with respect to the fluid flow with a certain amplitude and frequency. The velocity and acceleration of the model ship are calculated using the kinematic relationships and the forces and moment on the model ship are computed in a time period while the model ship drift angle is changing. The method is named dynamic oblique towing test (DOTT) and is applied to a container model ship and a surface combat model. The hydrodynamic maneuvering derivatives are obtained by an optimized curve fitting using Genetic Algorithms. The results of the computation in coefficient derivation and maneuver simulation indicate the accuracy and time efficiency of the method.