4.2.3. Aeroacoustics Noise Model of OpenFAST

This report describes theory and application of a newly released model of OpenFAST to simulate the aeroacoustics noise generated by the rotor of an arbitrary wind turbine. OpenFAST is a fully open-source, publicly available wind turbine analysis tool actively developed at the National Renewable Energy Laboratory. The aeroacoustics model, which is also fully open source and publicly available, is based on work performed over the past three decades. Frequency-based models for turbulent inflow; turbulent boundary layer – trailing edge; laminar boundary layer – vortex shedding; tip vortex; and trailing edge bluntness – vortex shedding noise mechanisms are included. A simple directivity model is also included.

The noise models are exercised simulating the aeroacoustics noise emissions of the International Energy Agency Wind Task 37 land-based reference wind turbine. A code-to-code comparison between the implementation presented here and the implementation available at the Wind Energy Institute of the Technical University of Munich, Germany, is also presented.

The documentation here was derived from NREL Technical Report TP-5000-75731 by P. Bortolotti et al. (https://www.nrel.gov/docs/fy20osti/75731.pdf)

• 4.2.3.1. List of Acronyms
• 4.2.3.2. List of Symbols
• 4.2.3.3. Introduction
• 4.2.3.4. Aeroacoustics Noise Models
  • 4.2.3.4.1. Turbulent Inflow
  • 4.2.3.4.2. Turbulent Boundary Layer – Trailing Edge
  • 4.2.3.4.3. Laminar Boundary Layer – Vortex Shedding
  • 4.2.3.4.4. Tip Vortex
  • 4.2.3.4.5. Trailing-Edge Bluntness – Vortex Shedding
  • 4.2.3.4.6. Directivity
  • 4.2.3.4.7. A-Weighting
• 4.2.3.5. Model Verification
  • 4.2.3.5.1. Reference Wind Turbine
  • 4.2.3.5.2. Code-to-Code Comparison
  • 4.2.3.5.3. Model Usage
• 4.2.3.6. Conclusions
• 4.2.3.7. Using the Aeroacoustics Model in AeroDyn
  • 4.2.3.7.1. Main Input File
  • 4.2.3.7.2. Boundary Layer Inputs and Trailing Edge Geometry
  • 4.2.3.7.3. Observer Positions
  • 4.2.3.7.4. Turbulence Grid
• 4.2.3.8. References