TY - GEN
T1 - Noise control using adjoint-based optimization
AU - Wei, M.
AU - Freund, J. B.
PY - 2002
Y1 - 2002
N2 - Attempts to control the jet noise have been hampered by an insufficent understanding of its mechanisms, resulting in a reliance on trial-and-error experimentation to reduce noise. This paper aims to explore the noise mechanism using adjoint-based noise control in conjunction with a direct numerical simulation. A control problem is formulated with the objective of reducing acoustic intensity on a line in the sound field. The cost function that quantifies this is used to force the adjoint of the compressible flow equation, which are solved numerically in the same way we solve the flow equations. The adjoint variables provide the sensitivity of the noise, as we have specifically defined it, to changes in actuation. Using this approach, the noise radiated from a two-dimensional mixing layer with convective Mach number Mc = 0:4 and Reynolds number based on vorticity thickness Reω = 500 was reduced by 6.3dB. This flow is a model of the near nozzle region of a jet and generalization of the technique to a jet is straightforward. Despite the substantial reduction in the noise, the changes of the flow field are small, as seen by examination of the turbulence kinetic energy and the momemtum thickness before and after control is applied. We conclude that the controler makes subtle changes to the radiating portion of the flow without drastically altering its energetics. Our preliminary investigations into the nature of the automatically identified control reveal little of how it works.
AB - Attempts to control the jet noise have been hampered by an insufficent understanding of its mechanisms, resulting in a reliance on trial-and-error experimentation to reduce noise. This paper aims to explore the noise mechanism using adjoint-based noise control in conjunction with a direct numerical simulation. A control problem is formulated with the objective of reducing acoustic intensity on a line in the sound field. The cost function that quantifies this is used to force the adjoint of the compressible flow equation, which are solved numerically in the same way we solve the flow equations. The adjoint variables provide the sensitivity of the noise, as we have specifically defined it, to changes in actuation. Using this approach, the noise radiated from a two-dimensional mixing layer with convective Mach number Mc = 0:4 and Reynolds number based on vorticity thickness Reω = 500 was reduced by 6.3dB. This flow is a model of the near nozzle region of a jet and generalization of the technique to a jet is straightforward. Despite the substantial reduction in the noise, the changes of the flow field are small, as seen by examination of the turbulence kinetic energy and the momemtum thickness before and after control is applied. We conclude that the controler makes subtle changes to the radiating portion of the flow without drastically altering its energetics. Our preliminary investigations into the nature of the automatically identified control reveal little of how it works.
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U2 - 10.2514/6.2002-2524
DO - 10.2514/6.2002-2524
M3 - Conference contribution
AN - SCOPUS:85087188713
SN - 9781624101199
T3 - 8th AIAA/CEAS Aeroacoustics Conference and Exhibit
BT - 8th AIAA/CEAS Aeroacoustics Conference and Exhibit
PB - American Institute of Aeronautics and Astronautics Inc.
T2 - 8th AIAA/CEAS Aeroacoustics Conference and Exhibit, 2002
Y2 - 17 June 2002 through 19 June 2002
ER -