RANSE Modeling of the Oscillatory Flow Over Two-Dimensional Rigid Ripples

The oscillatory turbulent flow over two-dimensional ripples is numerically simulated. Both the profile of the ripples and the values of the parameters used in the present study are typical of vortex ripples at the bottom of sea waves. The flow is computed numerically by using a RANSE approach. The results show that, as the ratio between the fluid excursion and the ripple wavelength is increased, the vortex shed on one side of the ripple crest is no longer the mirror image of the vortex shed on the other side and the dynamics of the vortex structures becomes quite complex. Moreover, the formation of steady recirculating cells, which might distort the profile of ripples in an erodible bed, is observed. A horizontal steady streaming is also generated, whose positive/negative direction depends on the values of the parameters.