We studied several wave configurations: elastic waves in a vibrating plate, capillary waves at the surface of water in small wave tanks (half a meter size), gravity surface waves in a large pool (13m in diameter) and a linear wave tank (36m long) and internal waves in the bulk of stratified water (which density is varying vertically as in the ocean or the atmosphere). In all these systems we have developed an imaging system that can record the wave field in 1D, 2D or 3D and with good temporal resolution. For the elastic plate and capillary waves we use a profilometry technique and a high speed camera (250 frames/s for capillary waves, 10000 frames/s for the vibrating plate). For the surface gravity waves in 2D in the 13m wave tank we developed a stereoscopic technique using 3 high resolution cameras and in the 36 m 1D wave flume we use a set of 8 synchronized cameras to record the wave elevation over 16m long. A part of the work was also to develop schemes to excite the waves. Large databases have being built in each of these experiments. For the case of internal waves, we use all the unique capabilities of the Coriolis facility for the study of geophysical flows in stratified and/or rotating fluids. The density of water is varied by dissolving large quantities of salt. The facility is filled with water whose density is decreasing with altitude up to 1m deep (about 110 tons of water and 2 tons of salt). Large amplitude waves are generated by oscillating vertical panels so that to generate a 3D nonlinear regime of interacting waves. This regime shares physical parameters with turbulence in the interior of the ocean.
We used high order statistical analysis to identify the wave coupling in these turbulent waves and compare them to the theoretical predictions. We investigate the effect of altering the physical conditions such as changing the water depth for water waves or adding stress to the vibrating plate. For instance, for capillary waves, we observed a clear transition from a wave turbulence state to a solitonic regime at low depth. In contrast, applying stress to the vibrating plate does not lead to such a change although the main effect is also to reduce the dispersion of the waves. For gravity waves we are also working on the distinction between 3-wave or 4-wave coupling and the influence of bound waves. In the 36m long wave flume we observed a promising regime of soliton gaz: solitons are localized propagating structures that interact by collisions that are also encountered in the propagation of light in optical fibers. We were able to set up a random regime involving a large number of interacting solitons.
These results led to publications in international journals and communications in international conferences.
