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This study introduces an efficient framework to reduce propeller tonal noise for urban air mobility. The method significantly cuts computational costs while achieving a 3-dB noise reduction.

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Area of Science:

  • Acoustics
  • Computational Fluid Dynamics
  • Aerospace Engineering

Background:

  • Tonal noise from propellers is a significant concern for urban air mobility (UAM) applications.
  • Efficient methods are needed to optimize propeller designs for noise reduction without extensive computational resources.

Purpose of the Study:

  • To develop and validate an efficient optimization framework for reducing isolated propeller tonal noise.
  • To enable significant computational savings by utilizing a steady-state formulation.

Main Methods:

  • Coupling Ffowcs-Williams-Hawkings (FWH) acoustic analogy with Reynolds-averaged Navier-Stokes (RANS) equations.
  • Utilizing the open-source su2 solver in a rotating reference frame (RRF) for steady-state simulations.
  • Employing a discrete adjoint solver for sensitivity analysis and automatic shape optimization.

Main Results:

  • Achieved a 3-dB reduction in upstream sound pressure level (SPL) while maintaining thrust.
  • The RRF-based tonal noise prediction closely matched time-resolved simulations.
  • The optimization consistently identified blade tips as critical noise-generating regions.

Conclusions:

  • The proposed steady-state RANS-FWH framework is effective for optimizing propeller designs to reduce tonal noise.
  • This approach offers significant computational advantages over unsteady simulations for UAM applications.
  • Blade tip geometry is a key factor in mitigating propeller tonal noise.