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- Title
RANSE Modeling of the Oscillatory Flow Over Two‐Dimensional Rigid Ripples.
- Authors
Sishah, B.; Vittori, G.
- Abstract
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. Plain Language Summary: Close to the coastline the sea bottom is often covered with small‐scale undulations called "ripples." Such bedforms play a relevant role in the nearshore circulation and in morphodynamic phenomena. Indeed, ripples influence the cross‐shore steady velocity component which is present close to the coast. Moreover, they influence the transport of sediment in the cross‐shore direction and hence the erosion rate of the coastline. In the present investigation we use a numerical model to compute the steady velocity component which is generated by the presence of ripples at the sea bottom. It will be shown that the steady cross‐shore velocity component can be directed either onshore or offshore, depending on the values of the parameters. Moreover, this steady velocity component turns out to be an order of magnitude stronger than that generated over a plane bottom. Key Points: The turbulent flow generated by an oscillating pressure gradient with zero mean is computed by means of a turbulence modelDepending on the values of the parameters of the problem, the flow field is not symmetric with respect to the ripple crestSteady velocity components form, which influence the sediment transport and are relevant in shaping the ripple profile
- Subjects
RIPPLES (Fluid dynamics); OCEAN waves; COMPUTER simulation; FLUX-line lattice; SEDIMENT transport
- Publication
Journal of Geophysical Research. Oceans, 2022, Vol 127, Issue 1, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2021JC017439