Low Frequency Waves Detected in a Large Wave Flume under Irregular Waves with Different Grouping Factor and Combination of Regular Waves

Luigia Riefolo,Guido Benassai,Fabio Dentale,Pasquale Contestabile

doi:10.3390/w10020228

Abstract

This paper describes a set of experiments undertaken at Universitat Politècnica de Catalunya in the large wave flume of the Maritime Engineering Laboratory. The purpose of this study is to highlight the effects of wave grouping and long-wave short-wave combinations regimes on low frequency generations. An eigen-value decomposition has been performed to discriminate low frequencies. In particular, measured eigen modes, determined through the spectral analysis, have been compared with calculated modes by means of eigen analysis. The low frequencies detection appears to confirm the dependence on groupiness of the modal amplitudes generated in the wave flume. Some evidence of the influence of low frequency waves on runup and transport patterns are shown. In particular, the generation and evolution of secondary bedforms are consistent with energy transferred between the standing wave modes.

Highlights

Extreme storms may significantly affect the coastal environment, especially in terms of erosion and sediment transport
Low-frequency waves can be generated from intense interaction between short waves and between short waves and long waves at the surf-swash boundary [5,6]
Cross-shore standing long wave swash oscillations are usually forced by infragravity frequency (f < 0.05 Hz) waves [7,8,9,10,11,12,13,14] as are swash oscillations due to waves traveling or oscillating along the water edge, parallel to the mean-water line [15,16,17,18,19]

Summary

Introduction

Extreme storms may significantly affect the coastal environment, especially in terms of erosion and sediment transport. They can provoke disastrous consequences such as sediment transport beyond the surf zone to unusual depths [1]. Waves reaching a coastline release the majority of their energy and momentum within the surf zone as intense turbulence generated at the front face of the breaker. Low-frequency waves can be generated from intense interaction between short waves and between short waves and long waves at the surf-swash boundary [5,6]. Wind-waves or short-waves (typical frequency of about 0.1 Hz) are the major force behind the swash zone (SZ)

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Methods

Conclusion