ESTIMATION OF THE NATURAL ROLL FREQUENCY OF A SHIP IN A CONFUSED SEA

The natural roll frequency of a ship in a confused sea has been estimated from analysis of the roll history. The estimator was defined, the sources of error were identified, and the parameters of the analysis were selected to minimize the variance of the estimator. The probability distribution was derived for the estimator of the natural roll frequency assuming a Pierson-Moskowitz spectral form for the sea. Bias in the estimator resulting from the steepness of the wave-slope spectrum in the vicinity of resonance and from the finite bandwidth and sidelobe structure of the spectral window was examined. The results of the theoretical analysis were confirmed by cumulative distribution functions computed from three 4-hr records from the roll history of a light cruiser. Correlations are presented of the estimated natural roll frequency with linear dimension and displacement for a variety of American naval vessels. (Author)

• Corporate Authors:

  Naval Research Laboratory

  4555 Overlook Avenue, SW
  Washington, DC  United States  20375-5320
• Authors:
  • Reid, W G
• Publication Date: 1977-4-4

Media Info

• Pagination: 80 p.

Subject/Index Terms

• TRT Terms: Cruisers; Damping (Physics); Military vessels; Ocean waves; Probability; Resonance; Rolling; Ship motion; Spectrum analysis; Stability (Mechanics); Stochastic processes; Wave measurement
• Old TRIS Terms: Roll; Roll amplitude; Sea states; Wave slope measurement
• Subject Areas: Data and Information Technology; Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00159075
• Record Type: Publication
• Source Agency: National Technical Information Service
• Report/Paper Numbers: NRL-8070 Final Rpt.
• Files: TRIS
• Created Date: Aug 31 1977 12:00AM