Longitudinal Motions of Taut Moorings

by Tokuo Yamamoto, (A.M.ASCE), Res. Engr.; Dept. of Civ. Engrg., Oregon State Univ., Corvallis, OR,
John H. Nath, (M.ASCE), Prof.; Dept. of Mech. Engrg./Oceanography; and Dir., Envir. Fluid Lab., Oregon State Univ., Corvallis, OR,
Charles E. Smith, Assoc. Prof.; Dept. of Mech. Engrg., Oregon State Univ., Corvallis, OR,

Serial Information: Journal of the Waterways, Harbors and Coastal Engineering Division, 1974, Vol. 100, Issue 1, Pg. 35-50

Document Type: Journal Paper


A general theory of the dynamic response of taut, elastic line buoy moorings to ocean waves was developed including the external hydrodynamic damping. A method to estimate the coefficient of skin friction on moorings was also developed. The range of the coefficient for the common ocean mooring lines was determined to be from 0.007 to 0.018. From numerical calculations for a surface-following type buoy moored with nylon rope, it was determined that the hydrodynamic damping can completely suppress resonance. In the heavily damped condition produced by large waves for relatively deep water mooring, it was found that only the upper part of the mooring line is in motion; and the dynamic tension at the buoy becomes large and proportional to the wave frequency, the 3/2 power of the wave height, and the square root of the skin friction coefficient on the mooring line, but independent of the whole length of the mooring line.

Subject Headings: Mooring | Ocean waves | Damping | Motion (dynamics) | Hydrodynamics | Skin friction | Hydro power | Dynamic response

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