Experimental investigation of the turbulent cascade development by injection of single large-scale Fourier modes

The current work presents an experimental investigation of interactions between flow scales. Injecting a single Fourier mode into a round jet flow made it possible to isolate and analyze the generation process of the high spectral components along the downstream flow development and to measure when they eventually are absorbed into the fully developed turbulence. Furthermore, an interesting dynamic evolution of the measured power spectra has been observed that confirms the cascaded delays reported by Josserand et al. 2017. Lately, these cascade delays have also been derived directly from a one-dimensional interpretation of Navier-Stokes equations described in a companion paper. The results in the current work provide vital information about the time scales in the triad interaction process.