AN EXPERIMENTAL AND NUMERICAL STUDY OF NONLINEAR INTERNAL WAVES

Nonlinear internal waves were measured on the large rotating platform at the Institut de Mecanique de Grenoble (I.M.G.). The experimental da ta complement the results presented in Renouard et al. [J. Fluid Mech. 177, 381 (1987)] and support the assumption that the solitary Kelvin wave is accompanied by Poincare waves. Based on the assumption of weak nonlinear, dispersive, and rotational effects, governing equations of the Boussinesq type are derived to model the evolution of an initial disturbance in a two-layer rotating fluid. The numerical study is base d on these equations which are analogous to the Boussinesq equations o f shallow-water theory and are not constrained to almost unidirectiona l propagation. Comparison of numerical solutions of the equations and experimental results are very good for moderately nonlinear conditions . These results provide supporting evidence for the resonant interacti on of nonlinear Kelvin waves and linear Poincare waves, as described b y Melville et al. [J. Fluid Mech. 206, 1 (1989)].