Laboratory studies of wind‐driven Langmuir circulations

Abstract

Langmuir circulations in a wind wave tank have been observed and measured by a variety of methods including dye patterns and floating surface tracers. On the basis of measurements of cellular wavelength λ c as a function of surface wavelength λ w and depth H a tentative functional relation for the dependence of λ c / H upon λ w / H is proposed. The experiments clearly imply that the waves play an important role in the mechanism of formation of the Langmuir circulations but that the depth of the layer has a significant modifying influence. On the basis of certain ‘rake’ experiments and other indirect observations it is proposed that when λ w / H < 1, the primary scale of Langmuir circulations, related to λ w , transfers energy to a larger scale that is commensurate with the depth such that λ c / H ≃ 2. Under these circumstances, two distinct scales of Langmuir circulations may exist simultaneously.