Tue April 27th 2010
HR W121
Seminar Instability wave models of turbulent jets
Kristján Guðmundsson


We study pressure and velocity fluctuations associated with large-scale coherent structures in turbulent jets from round and serrated nozzles.
Large-scale disturbances to the turbulent mean flow are modeled via linear
stability analysis (LST) and the Parabolized Stability Equations (PSE).
We show that PSE provides better agreement with near-field microphone-array
data at low frequencies than previous models based on LST. We examine the extent to which microphone data is contaminated by fluctuations uncorrelated with large-scale structures. By filtering out the uncorrelated fluctuations, via the proper orthogonal decomposition (POD), better agreement between data and theory is obtained. We next project PSE predictions onto a basis of POD-modes constructed from instantaneous cross-stream PIV measurements, finding excellent agreement inside the jet. We conclude that instability wave models provide an accurate description for the near-field large-scale fluctuations of turbulent jets, provided the turbulent mean flow is used in the calculation.
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The 10th Complex Motion in Fluids 2021
Max Planck Gesellschaft
Centre for Scientific Computing