An experimental search for classical second sound in a system of nonlinear random waves

Abstract

A nonlinear medium driven far from equilibrium by the input of energy in the form of mechanical wave motion becomes wave turbulent. The steady state corresponds to a power spectrum with a low-frequency dependence that is characteristic of the particular system [A. Larraza and S. J. Putterman, in Irreversible Phenomena and Dynamical Systems Analysis in Geosciences (Reidel, Dordrecht, The Netherlands, 1987), p. 139]. It has been shown [A. Larraza and S. J. Putterman, Phys. Rev. Lett. 57, 2810 (1986)] that the wave turbulence can be elastic, so that its energy fluctuations, instead of diffusing, propagate as waves, in analogy to (thermal) second sound in superfluid helium. Experiments in a wind-driven wave tank will be described that are designed to measure the theoretical predicted second sound mode for a random field of short, deep-water gravity waves [Larraza et al., Phys. Rev. A (March 1990)], by use of dual-channel capacitive wave staff and a “probe wave” generated by a hydraulically actuated plunger. [Work supported by the NPS Direct Funded Research Program.]