Triadic nonlinear interactions and acounstics of forced versus unforced turbulent jets

Abstract

We explore the potential of bispectral mode decomposition (BMD) for physical discovery in jet flows. BMD is a modal decomposition that is tailored to the extraction of flow structures involved in triadic interactions. Large-eddy simulations (LES) of turbulent forced and unforced round jets at Re = 50,000 and Mj = 0.4 are conducted and validated with the companion experiment at the Institut Pprime. The comparative BMD analysis reveals that triadic interactions in both forced and unforced jets are most prevalent in a welldefined region near and downstream of the closure of the potential core. A BMD analysis of far-field pressure sheds light on the previously reported observation that differenceinteractions are more efficient radiators of jet noise than the sum-interactions.

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