I am not so clear the use of freestream velocity in FWH equation when helicopter rotor was in forward flight condition and observer position was fixed relative to the rotor.
The description of the problem is that when i use the CFD information on blade surface as the input for non-porous FWH equation, where is the freestream velocity used, is it used for the correction of surface velocity?
Hello DR JINBIN! The following links have been ferreted out , germane to your question:
http://www.bu.edu/ufmal/files/2011/08/tutorial.pdf
A novel porous Ffowcs-Williams and Hawkings acoustic ...
conservancy.umn.edu › bitstream › handle
PDFby Z Nitzkorski - 2015 -
http://www.delegia.com/app/data/8684/Abstract/28570/ETC16_Cianferra.pdf
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050182105.pdf
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/ffowcs-williamshawkings-equation-for-hydroacoustic-analysis-of-rotating-blades-part-1-the-rotpole/9580ECACCC7F9F05739AFA35AD240096
I I hope this input facilitates you in your work. Best regards--
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