Data-educed broadband equivalent acoustic source model for supersonic jet noise.

Area of Science:

• Acoustics
• Fluid Dynamics
• Aerospace Engineering

Background:

• Modeling jet noise requires accounting for complex spatiospectral variations.
• Broadband equivalent acoustic source distributions are essential for accurate sound field prediction near high-speed jets.

Purpose of the Study:

• To present a novel technique for creating broadband equivalent source distributions by spectrally decomposing turbulent mixing noise.
• To model both large-scale and fine-scale turbulent mixing noise components separately for improved acoustic modeling.

Main Methods:

• Utilized spectral decomposition to separate large-scale (wavepackets) and fine-scale (incoherent sources) turbulent mixing noise.
• Applied a frequency-dependent approach for both wavepacket and incoherent source modeling.
• Validated the technique using acoustical measurements from an unheated Mach 1.8 jet.

Main Results:

• The combined wavepacket and incoherent source model accurately represents the jet's sound field for Strouhal numbers from 0.04 to 0.25.
• Wavepackets alone adequately modeled sound levels in the maximum radiation region.
• An additional incoherent source distribution was necessary for accurate predictions at other locations.

Conclusions:

• The developed broadband equivalent acoustic source representation effectively models high-speed jet noise.
• Accounting for a frequency-dependent shift in the apparent acoustic source region improves model accuracy at higher Strouhal numbers.
• The frequency-dependent source region's importance increases closer to the jet, particularly in the near field.