Journal of Fluid Mechanics

Modulation of three resonating gravity–capillary waves by a long gravity wave

Karsten  Trulsen a1 and Chiang C.  Mei a1
a1 Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

Article author query
trulsen k   [Google Scholar] 
mei cc   [Google Scholar] 


We consider a resonant triad of gravity–capillary waves, riding on top of a much longer gravity wave. The long-wave phase is assumed to vary on the same scale as the slow modulation of the short waves. Envelope equations are first deduced in the Lagrangian description. By perturbation analysis for a weak long wave, we then find that the long wave can resonate the natural modulation oscillations of the triad envelope, giving rise to various bifurcations in the Poincaré map. Numerical integration for a stronger long wave reveals that chaos can emerge from these bifurcations. The bifurcation criterion of Chen & Saffman (1979) for collinear Wilton's ripples is generalized to arbitrary non-collinear triads, and is found to play an important role as a criterion for the onset of chaotic behaviour.

(Published Online April 26 2006)
(Received April 25 1994)
(Revised November 18 1994)