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Research Papers

# Generation of Large Angle Bimodal Sea States Using One-Side Segmented Wavemaker

[+] Author and Article Information
P. Roux de Reilhac, F. Bonnefoy

Centrale Nantes, LMF-UMR CNRS 6598, Nantes 44321, France

P. Ferrant

Centrale Nantes, LMF-UMR CNRS 6598, Nantes 44321, Francepierre.ferrant@ec-nantes.fr

J. Offshore Mech. Arct. Eng 130(3), 031008 (Jul 16, 2008) (10 pages) doi:10.1115/1.2904953 History: Received July 13, 2007; Revised December 19, 2007; Published July 16, 2008

## Abstract

In the present work, we study the capabilities of a one-side segmented wavemaker to generate multidirectional sea states. We want to reproduce typical West Africa sea conditions in a rectangular basin, that is, two spectra representing swell and wind waves with $±45deg$ main directions relative to the basin axis. For that purpose, we study two generation techniques proposed, respectively, by Dalrymple and Molin which rely on the control of sidewall reflections in order to enlarge the testing zone. Both numerical and experimental results show that the use of such methods in combination with a one-side wavemaker provides high quality wave fields as well as large extent testing area. The Molin method appears to be more efficient in terms of wave field quality within the testing area although the tuning of its setting parameters requires more care than the Dalrymple method.

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## Figures

Figure 1

Basin equipped with left: one-side segmented wavemaker, right: two-side segmented wavemaker

Figure 2

Rectangular wave basin

Figure 3

Error (in percent) on target amplitude for snake principle, Dalrymple method, and disk method (from top to bottom)

Figure 4

Amplitude at the fundamental frequency for 45deg regular wave, left: Dalrymple method, right: Molin method

Figure 5

Normalized amplitude ηmax∕a and quality index Q against disk radius R̃

Figure 6

Weighting coefficients for the quality index Q: P1⪡P2⪡P3

Figure 7

Evolution of the normalized radius R̃

Figure 8

Quality index with top: Dalrymple method and bottom: disk method

Figure 9

Wave field error on the free surface (in percent)

Figure 10

Spectral density of wave elevation, nondimensionalised by Stargetmax

Figure 11

Target (in solid lines) and measured (in contour levels) directional wave spectrum; Dalrymple method (the dashed line is the Biésel limit)

Figure 12

Target (in solid lines) and measured (in contour levels) directional wave spectrum; Molin method (the dashed line is the Biésel limit)

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