Large eddy simulation of turbulence flow noise on streamers
Paper in proceedings, 2009
A Large Eddy Simulation (LES) approach has been used to compute the turbulence flow structures surrounding a towed marine streamer. The time-dependent and three-dimensional calculations in the LES have high resolutions both in time and space, making it possible to directly sample statistics and predict the flow noise spectrum on a streamer. While flow noise is hardly the only mechanical noise source in a streamer, it is often the dominant noise source for low-to-medium frequencies in a quite environment. For example, the simulations presented in this paper together with data made public from a commercial dual-sensor streamer towed in moderate weather conditions at 7m, 15m, and 20m depth suggests that the turbulence flow noise is the dominant noise source up to ∼40 Hz in the cases of 15m and 20m towing depth. Because rather few streamer designs are published, as an example this paper analyzes a solid streamer with a hydrophone carrier based on the drawing presented in Dowle & Maples. It is shown that the length of the hydrophone carrier affects noise levels as well as the shape of the spectrum. Moreover, since the membrane of the hydrophone carrier is flexible, it is necessary to also take fluid-structure interaction into account because resonance of the membrane might be triggered at its eigenfrequencies, which would increase the flow-induced noise levels significantly. Finally, results from calculations of a streamer in a cross-flow are shown.