Title

NON-NORMAL DESCRIPTIONS OF MORISON-TYPE WAVE FORCES.

Document Type

Article

Date of Original Version

1-1-1987

Abstract

The usual description of the force exerted by a stochastic wave is extended to include the non-normality of that force. In particular, the J. R. Morison equation is used to describe the force resulting from a sea state with stationary, normally distributed water velocities. Thus, the force non-normality which is considered results only from the nonlinearity of the Morison equation. The fourth order cumulant function is used to describe the non-normality of the force. The same information is also represented as a three-dimensional spectral density, which results from a three-fold Fourier transform of the cumulant function. Closed form solutions are not found, but the results of a power series expansion method appear to give good approximations. Potential applications of the results involve determinations of the non-normality of the response of a structure subjected to a Morison-type wave force. Such response non-normality can then be used to substantially improve estimates of structural failure, due to either first passage or accumulation of fatigue damage.

Publication Title

Journal of Engineering Mechanics

Volume

113

Issue

2

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