Abstract

The direct wave attenuation influence of surface active compounds on plunger-generated water waves (1.0, 1.3, 1.8, 2.0, 2.3, and 2.5 Hz) was investigated in the Hamburg wind-wave tunnel by systematic variation of the hydrophilic group. Long-chain alcohols, acids, and amines exhibit a considerable wave damping effect. An additional wave energy dissipation term is active in the presence of carboxylic acid ester (E/Z-isomerization). It is concluded from the experimental results that hydrophobic interactions between the hydrophobic alkyl chains and the adjacent water layer play a dominant role by inducing “ice-like clathrate structures.” Some hydrophilic groups (mono- and di-oxyethylenated alcohols) may also promote formation of these structures, whereas other hydrophilic groups (sodium sulfonates; poly-oxyethylenated alcohols with nglycol ≥ 3) are counteracting against this effect (“structure breakers”), which results in a considerably lower wave attenuation effect. Proteins and triglycerides exhibit no significant wave damping ability, while sterols, and hydrophobized amino acids and carbohydrates in part show wave damping characteristics similar to those of long-chain alcohols. The experimental results are discussed in the framework of theories developed by Cini et al. (1983) and by Lucassen-Reynders and Lucassen (1969) with emphasis upon the so-called “Marangoni-effect,” which appears to be of highly dissipative character

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