3D wave-current modelling : a model for secondary circulations#report

Surface waves propagating with a mean current can induce series of vortex pairs with horizontal axes. This phenomenon is called Langrnuir circulation and it induces vertical transport of horizontal momentum as well as of dissolved or suspended matter in the top layer of lakes, reservoirs and seas. Langrnuir circulation can be simulated numerically, but it demands significantly smaller grids then achievable in large-scale simulations of coastal seas. Therefore, Radder (1998) proposed a theoretical model for vertical momentum exchange, i.e. Reynold stresses, by Langrnuir circulation. This model depends on mean-current and on surface-wave properties and the model is without free (calibration) coefficients. The present report is concerned with a check the algebra as well as the suppositions of Radder's (1998) model. The main conclusion is that Radder derived his model correct, just minor alterations to his suppositions were considered.