Experimental investigation on the characteristics of directional focusing waves

The analysis on fixed or floating structures exposed to directional extreme waves has been a topic of keen interest in ocean engineering. In this context, an attempt is made to study the characteristics of laboratory generated directional rogue waves, termed also as focusing waves. The first-order w...

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Bibliographic Details
Published in:Proceedings of the Institution of Mechanical Engineers. Part M, Journal of engineering for the maritime environment Journal of engineering for the maritime environment, 2023-02, Vol.237 (1), p.20-36
Main Authors: Lakshman, Rajagopal, Sriram, Venkatachalam, Sundar, Vallam
Format: Article
Language:English
Subjects:
ATP
Bandwidths
Breakers
Breaking waves
Broadband
Directional spectra
Extreme waves
Floating structures
Frequency spectra
Frequency spectrum
Maximum likelihood method
Nonlinear systems
Nonlinearity
Ocean engineering
Offshore engineering
Parameters
Slopes
Spectrum allocation
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Summary:The analysis on fixed or floating structures exposed to directional extreme waves has been a topic of keen interest in ocean engineering. In this context, an attempt is made to study the characteristics of laboratory generated directional rogue waves, termed also as focusing waves. The first-order wave paddle displacements were generated using the linear superimposition principle by applying a constant steepness spectrum associated with directional components. The phase angles are set to be constant at a predefined location to create an extreme event. The experimental test cases span from narrow to broadband spectra having two central frequencies, namely, 0.68 and 0.85 Hz. The bandwidth ratios of 0.5 and 0.75 were considered with five discrete directions ranging from −25°to 25°. The tests include spilling breakers and non-breaking waves. The investigation involves studying the variations in the Atiltness parameter (ATP), Crest height ratio, and the nonlinearity parameter provided by Hastings, an index to measure the effect of nonlinearity. In addition, directional studies using the maximum likelihood method (MLM) are also presented. The critical combination of frequency spectrum and bandwidth is identified from the focusing wave characteristics and discussed in this paper for the tested conditions. The shift in directional spectrum due to nonlinearity was noticed in the present study.
ISSN:1475-0902
2041-3084
DOI:10.1177/14750902221115953