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Effect of nonlinearities on the frequency response of a round jet

Qadri, UA and Schmid, PJ (2017) Effect of nonlinearities on the frequency response of a round jet. Physical Review Fluids, 2.

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© 2017 American Physical Society. We investigate the effect of nonlinearities on the frequency response of a round, incompressible jet. Experiments show that axisymmetric structures dominate the response of forced and unforced jets. In contrast, linear stability and frequency response analyses predict the asymmetric mode (m=1) to be locally more unstable and globally more amplified than the axisymmetric mode (m=0). We perform a weakly nonlinear expansion of the response of the flow to harmonic forcing and derive an asymptotic expression for the sum of this divergent series beyond its limit of validity. This expression compares reasonably well with the nonlinear gain up to forcing amplitudes an order of magnitude greater than the limit of validity of the weakly nonlinear expansion. For equal forcing amplitudes, the asymmetric mode dominates over the axisymmetric mode. This suggests that the projection of environmental forcing onto the individual azimuthal modes plays an important role in the preferred dynamics of round jets.

Item Type: Article
Divisions: Div A > Energy
Depositing User: Cron Job
Date Deposited: 05 Nov 2018 20:22
Last Modified: 13 Apr 2021 07:30
DOI: 10.1103/PhysRevFluids.2.043902