Near-critical fluids as experimental models for geophysical flows:: The case of internal gravity waves

We perform a theoretical analysis of internal gravity waves in near-critical fluids to determine whether they have the same behavior as in classical fluids. Two points are studied: the relevance of classical incompressible equations and the possibility of a coupling between internal gravity waves and the piston effect. Using asymptotic analysis of Navier-Stokes equations, it is shown that incompressible equations are applicable even very close to the critical point, and that the piston effect and internal gravity waves never couple, unlike what happens in the case of forced oscillations. These two conclusions confirm the relevance of using near-critical fluids to simulate internal gravity waves in large geophysical systems. (C) 2001 American Institute of Physics.