Turbulence Induced by Storm Waves on Deep Water

Abstract

Results of laboratory and field experiments performed in November–December, 2014 to study turbulence induced by wave motion are represented. Elevations of free sea surface and fluctuations of three components of water particle velocity are synchronously measured at calm conditions when wave breaking is absent. The data is obtained in the ranges of wave and turbulence frequencies, and in the depth range from the surface to half a length of surface waves. A method for separating the measured velocity fluctuations into at a wave and two turbulence components (the one is induced by wave motions and another is a background hydrodynamic turbulence) is developed. In field experiments the bound frequency of ~0.8 Hz had been determined. The coherence of the turbulent fluctuations and sea surface elevations sharply decreases above this frequency. Direct instrumental measurements confirmed stratification of a wave flow into a near-surface turbulent layer induced by wave motion and an underlying layer with the background hydrodynamic turbulence. The characteristics of turbulence in a near-surface layer are connected linearly with magnitude of envelope of vertical component velocity. This fact enables to attribute the turbulent fluctuations in this layer to wave-induced turbulence. Based on analysis of experiments the conclusion about existence of wave-induced turbulence in absentia other sources of turbulence such as wave breaking, wind stresses and Langmuir circulations is drawn.

Keywords

wave induced turbulence, background turbulence, field experiment, storm waves.

DOI: 10.22449/1573-160X-2015-5-22-31

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