Effect of Short-Crested Seas on Quadratic Response.
Abstract
The motivation of the present work was that, in contrast to the situation for linear seakeeping phenomena, there appeared at present, there seems to be no theory for estimating common statistical parameters for quadratic nonlinear seakeeping systems sujected to short-crested randum directly from electronics and communication theory where the notion of short crestedness does not exist, and thus it is a 'time only' (long crested sea) model. Broadly, the fundamental difference between the time only and the present short-crested sea model is that a wave field rather than a wave profile must be dealt with. The result is that the linear and quadratic response functions which define the ship dynamics become functions of vectors rather than scalars. Given a directional wave spectrum and the linear and quadratic response functions corresponding to some response of interest, estimating formulae were developed for a variety of statistics. When compared corresponding results for the time only quadratic model, there were no real surprises in the short-crested estimation formulae, only the greather complication which must be expected because of the increase in the dimension of the problem. It was found that, there is no necessity to work in the encounter domain. Results imply that the previous restriction of the time only case to the encounter frequency domain may be largely removed. The formula for the mean value of the response in short-crest seas is especially simple, in that it is hardly more computationally demanding than estimating the variance of a purley linear system in short-crested seas. Keywords: Random processes; and Quadratic nolinearities.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1985
- Accession Number
- ADA163435
Entities
People
- John F. Dalzell