RECENT ADVANCES IN THE SEAKEEPING ASSESSMENT OF SHIPS

• Published in: Naval Engineers Journal
• Main Authors: McCREIGHT, KATHRYN K., STAHL, RALPH G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1985
• Subjects: Pacific; North Atlantic
• Online Access: http://dx.doi.org/10.1111/j.1559-3584.1985.tb01357.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1559-3584.1985.tb01357.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1559-3584.1985.tb01357.x

ABSTRACT Three factors affect the operability of a ship in a seaway: the motion characteristics of the ship, the environment, and the mission requirements. A method is presented which predicts the operability of a ship at specific geographical locations. Analysis of operability is carried out using transfer functions which represent the motion characteristics of a ship, wave data for the North Atlantic and for the North Pacific, and limiting motion criteria for a specific mission. From these three factors, operability indices are developed. Operability indices include the percent of time of operation (PTO) and the limiting significant wave height (LSWH). Contours which describe bands of constant values of the percent of time of operation for a mission are determined. In developing the indices and resultant contours, operability in the presence of each of a large number of wave spectra is weighted according to probability of occurrence of that wave spectrum. The probability of occurrence of wave spectra for the winter and for the entire year for 57 points in the North Atlantic and 21 points in the North Pacific is used for various combinations of significant wave height and spectral modal period. Composite wave data for the general North Atlantic or general North Pacific also are utilized. The operability for mobility criteria of six hullforms ranging in displacement from approximately 3,000 to 9,000 tons is compared. Both monohull and SWATH configurations are considered. Comparison of operability as a function of significant wave height, as a function of displacement, and as a function of speed is made using winter and annual wave statistics for the general North Atlantic. Some results also are presented for the general North Pacific. Operability contours for the North Atlantic are presented for the hullforms. Tabulated limiting significant wave heights for various operating conditions are presented. The effect of systematic variations in performance criteria on performance is presented as a function of speed.