Experimental Study of Undertow and Turbulence Intensity Under Irregular Waves in the Surf Zone

by Nels J. Sultan, Texas A&M Univ, College Station, United States,
Francis C. K. Ting, Texas A&M Univ, College Station, United States,

Document Type: Proceeding Paper

Part of: Ocean Wave Measurement and Analysis


Experiments are performed in a two-dimensional wave tank with a sloping beach. Irregular waves are generated and the water particle velocity is measured in the surf zone with a laser Doppler velocimeter. Using ensemble averaging, the turbulent kinetic energy, k, times series is then calculated. Results are compared with previously published experiments using regular waves. There is a significant temporal variation of k throughout the surf zone. However, k, is more uniform at points closer to the shoreline. Further from shore k is more intermittent and discrete `bursts' of k caused by individual breaking waves seem to decay in an exponential manner. The use of ensemble averaging to study turbulence under irregular waves is found to be feasible although consuming.

Subject Headings: Random waves | Undertow | Turbulence | Irregular waves | Surf zones | Breaking waves | Wave tanks | Wave velocity

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