Observing and estimating of intensive triad interaction occurrence in very shallow water. (1st July 2016)

• Record Type: Journal Article
• Authors: Mahmoudof, Seyed Masoud; Badiei, Peyman; Siadatmousavi, Seyed Mostafa; Chegini, Vahid
• Is Part Of: Continental shelf research. Volume 122(2016)
• Page Start: 68
• Page End: 76
• Publication Date: 2016-07-01
• Subjects: Intensive triad interaction -- Spectral peak -- Bicoherence -- Field investigation; Continental shelf -- Periodicals; Submarine geology -- Periodicals; 551.41
• DOI: 10.1016/j.csr.2016.04.003
• Languages: English
• ISSNs: 0278-4343

Abstract

Abstract: In this study, a series of field measurements were carried out to investigate triad interactions of spectral peak in near shore. The water level fluctuations were recorded at 5 stations with depths varying from 0.8 to 5 m along a shore-perpendicular transect at sandy coasts of Nowshahr, located in the southern Caspian Sea coast. Two storms with significant wave height of approximately 1.4 m were observed during the measurement period. Using bispectral analysis, a new quantitative index is proposed to investigate temporal and spatial intensity of nonlinear interaction between spectral peak and other harmonics. The proposed index was evaluated for time series of water level data and compared with the bicoherence value of self-spectral peak triad interaction (SSPT); b 2 ( f p, f p ) . Comparing to SSPT, the proposed new index includes all positive and negative triad interactions with spectral peak. The relative depth, k p d, of non-breaking waves varied from 0.25 to 2.00 along the transect during the study period, where k p is the wave-number and d is the water depth. In general, SSPT increased by decreasing k p d ; however, the results showed that in two shallow stations the maximum SSPT did not correspond to the lowest values of k p d . A considerable time lag was observed between occurrence of the most intensive triad interactions and termination of wave breaking in post storm condition. Furthermore, the intensive triad interactions happened several hours after the largest Ursell numbers of non-breaking waves. Highlights: In very shallow water of the surf-zone near the swash and shore of sandy beaches. Time lag between intensive triad interactions of peak frequency and high non-breaking waves was observed. Significant triad interactions of spectral peak occur in the waning phase of storm. Maximum value of b 2 (fp, fp ) did not occur for minimum relative depth (kp d). No triad interaction when wave breaking was dominant.