Maneuvering Simulation Model Based oh Ship Design Parameters

Abstract

The knowledge of maneuvering characteristics of ships under different conditions is paramount from the safety and operation point of view. The maneuvering characteristics can be predicted in a number of ways: model scale maneuvering test, numerical calculation using hydrodynamic theories and numerical simulation based on semispherical formulas. The first and second approaches require detailed information of the hull geometry and other particulars. The model test prediction is often costly since it requires model construction, specialized equipment and testing facilities, etc. The theoretical prediction is less expensive than the model test but it usually requires substantial amount of computer resources, and CPU time in particular. On the other hand, semiempirical prediction does not require detailed ship information or extensive use of computer facilities, and it is the least expensive. However, it can only predict the general maneuvering characteristics for a given combination of ship basic parameters – principle dimensions, rudder and propeller particulars. Such general maneuvering characteristics would be essential for applications in ship design, port planning and maritime policy making. Using the semiempirical prediction at the early stage of a ship design, the designer can optimize the ship basic parameters in relation to maneuverability and other mission requirements. The port authorities and regulatory agencies can consult the semiempirical prediction in their decision making process regarding port development, traffic control and navigational requirements for different classes of ships. Bearing this in mind, a hydrodynamic derivative-type maneuvering simulation model has been developed at the Institute for Marine Dynamics ( IMD) of the National Research Council Canada. The development of the model was based on published information. The simulation model can predict the maneuvering characteristics of a ship if its hydrodynamic derivatives, rudder and propeller geometry are known. In addition, it can also predict maneuvering characteristics of merchant ships based on its basic design parameters including: length, beam, draft, block and waterplane coefficients, displacement, rudder and propeller geometry, etc. The model allows continuous engine speed and rudder angle inputs for simulation of both standard and arbitrary maneuvers. The model can also predict the influence of different propulsion systems and operating conditions oo the maneuvering behavior. It incorporates the effect of a bow thruster and the different response characteristic of steam and diesel power plants. In addition, the effects of bank and channel, current, shallow water and wind on the maneuvering behavior are incorporated. The mathematical formulations of the basic maneuvering model, thruster, propulsion plants and various environmental effects are described in Section 2 and 3. A carputer software package has been developed according to the mathematical formulations described. The package utilizes the existing carputer facilities at IMD. It is designed to be user-friendly and operates interactively according to the instructions of the user. The structure and usage of the simulation software are described in Section 4. A discussion of the accuracy of the simulation model is based on comparisons with model scale and sea trial results and the conclusions are presented in section 5 and 6, respectively.