We study experimentally the interaction of nonlinear internal waves in a stratified fluid confined in a trapezoidal tank. The setup has been designed to produce internal wave turbulence from monochromatic and polychromatic forcing through three processes. The first is a linear transfer in wavelength obtained by wave reflection on inclined slopes, leading to an internal wave attractor which has a broad wave number spectrum. Second is the broadbanded time-frequency spectrum of the trapezoidal geometry, as shown by the impulse response of the system. The third one is a nonlinear transfer in frequencies and wave vectors via triadic interactions, which results at large forcing amplitudes in a power law decay of the wave number power spectrum. This first experimental spectrum of internal wave turbulence displays a k −3 behavior.
Quadrant analysis was performed with instantaneous velocities measured by laser Doppler velocimetry in a zero pressure gradient supersonic turbulent boundary layer on an adiabatic or heated plate. The distributions obtained were close to those for subsonic flows, and were not modified by the wall heating. Moreover, this heating made it possible to extend the analysis to a part of the buffer layer that is characteristic of the turbulence process (y+∼15). This led to a differentiation between the effects of Reynolds and Mach numbers in the various regions of the boundary layer.
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