A nonlinear Schrödinger equation for water waves on finite depth with constant vorticity

Roland Thomas (1) , Christian Kharif (1) , Miguel Manna (2)

1 IRPHE - Institut de Recherche sur les Phénomènes Hors Equilibre
2 L2C - Laboratoire Charles Coulomb

A nonlinear Schrödinger equation for the envelope of two dimensional surface water waves on finite depth with non zero constant vorticity is derived, and the influence of this constant vorticity on the well known stability properties of weakly nonlinear wave packets is studied. It is demonstrated that vorticity modifies significantly the modulational instability properties of weakly nonlinear plane waves, namely the growth rate and bandwidth. At third order we have shown the importance of the coupling between the mean flow induced by the modulation and the vorticity. Furthermore, it is shown that these plane wave solutions may be linearly stable to modulational instability for an opposite shear current independently of the dimensionless parameter kh, where k and h are the carrier wavenumber and depth respectively.

Mots clés: finite depth; nonlinear Schrödinger equation; Gravity waves; vorticity

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Roland Thomas, Christian Kharif, Miguel Manna. A nonlinear Schrödinger equation for water waves on finite depth with constant vorticity. Physics of Fluids, 2012, 24 (12), pp.127102. ⟨10.1063/1.4768530⟩. ⟨hal-00716088⟩