SECONDARY INSTABILITIES IN LANGMUIR CIRCULATIONS

Finite-amplitude Langmuir circulation in the form of rolls parallel to the wind direction is shown to be subject to three-dimensional instab ility under certain circumstances. Density stratification is not requi red for instability to manifest. The preferred form of this secondary instability appears to be traveling waves propagating in the direction of the wind. These cause the rolls, and their surface windrows, to de viate from the wind direction by a small angle for which estimates are given. The results of the paper show the value of secondary stability results for the design of numerical experiments to simulate Langmuir circulation.