Ship Motion Response Research Articles

Complete Proceedings - Single PDF Download

These proceedings of the Eighteenth Coastal Engineering Conference held in Cape Town, Republic of South Africa, November 14-19, 1982 include the 167 papers presented at the conference. The proceedings are divided into 5 major subject areas. Part I, theoretical and observed wave characteristics, includes discussions on wave height distribution, waves in nearshore zones, tide predictions, wave energy conversion and wind effects. Part II, covers aspects of coastal sediment problems such as sediment transport, shore protection, beach profile changes, and beach erosion. Part III, coastal structures and related problems, covers construction, monitoring and performance of different coastal and offshore structures. Coastal, estuarine, and environmental problems are addressed in Part IV, including design of coastal water intakes, salinity intrusion, ocean outfalls, and environmental effects of construction. The final section covers ship motion response.

Application of Seakeeping Analysis

The paper gives a brief description of modern seakeeping analysis and discusses its application to problems encountered in engineering practice. The authors' experience with the computer program SCORES, for prediction, of ship motion responses, is reviewed, and examples of its application to typical problems are given. An appendix describes CARGO, a post-processing computer method developed to more fully utilize the motion response characteristics of the SCORES program.

Simulation studies of the response of deeply towed vehicle to various towing ship maneuvers

The behavior of a long cable towed at slow speeds through the ocean depends in a complex fashion on the path followed by the towing ship relative to the water. A cable simulation program was used to characterize the response of the cable by using idealized towing ship maneuvers as input to the program. The response of the cable was noted and it was found that the behavior of the cable was strongly dependent on the fundamental period of the towing vessel maneuvers. Sinusoidal deviations of the towing ship from a straight towing track resulted in delayed and reduced excursions of the towed vehicle from the tract; the estimated response ratio varied from 0·002 to 0·800, depending both on the period of the deviations (periods ranged from 5·5 to 4·0 hr) and on the towing depth (2 or 6 km). The ship's speed was 3 km/hr. The time lag between ship motion and vehicle response was approximately 0·5 hr for the shallow case and 1·3 hr for the deep case. Simulations runs of a low dragk (faired) cable showed that the behavior of the vehicle when towed at a depth of 6 km was similar to that obtained with a conventional cable at 2 km depth. The response of the towed vehicle to a right-angle turn of the towing ship was investigated and a generalized model of the response developed. The effects of a controllable side force on the towed vehicle were also simulated and it was noted that a deviation (2-hr period) of the towed vehicle from a straight-line track could be reduced from 40 to 2 m by impressing a side force on the vehicle with an average magnitude of 150 newtons (30 lb).

Analysis of roll stabilizer performance1

A short review of the mathematical formulation of the seaway and the ship motion responses with special reference to rolling is given, where as measures of effectiveness of roll damping devices are briefly discussed. Full scale rolling experiments with a motoryacht in still water and in waves are a nalyzed. The performance and design of fin-stabilizers is dealt with on the basis of experimental results and common hydrodynamic knowledge. The use of rudders as roll stabilizers seems to be rather promising according to full scale motoryacht experiments.

MECHANICAL SYSTEMS FOR OCEAN ENGINEERING

ABSTRACTThis paper will discuss mechanical handling systems associated with ocean engineering operations and limitations of present handling system in salvage and rescue operations including problem areas in handling of submersible vehicles and other large objects at sea. Ship motion and payload response to various sea conditions will be evaluated. Emphasis will be placed on the effect of relative motion and the associated dynamic loads imposed on the handling gear. Methods of motion compensation and load attenuation will be examined.