Accession Number : AD1018105


Title :   Acoustics of a Mixed Porosity Felt Airfoil


Descriptive Note : Technical Report


Corporate Author : NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI NEWPORT United States


Personal Author(s) : Hellum,Aren M


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/1018105.pdf


Report Date : 06 Jun 2016


Pagination or Media Count : 25


Abstract : Lifting surfaces produce noise in operation, and porous materials have been shown to reduce this noise. Acoustic measurements were made on three arrangements of poroelastic material: full-chord porosity, full-chord impermeability, and mixed porosity. A scaling scheme is presented that collapses the spectra acquired at different Reynolds numbers. The results are compared to applicable published data. The noise reduction produced by the mixed porosity arrangement is found to be similar to the fully-porous arrangement at low Reynolds numbers. The noise reduction produced by the mixed and fully-porous foils does not match over the entire frequency range at higher Reynolds numbers.


Descriptors :   Airfoils , noise reduction , porous materials , acoustic impedance , lifting surfaces , reynolds number , trailing edges , boundary layer


Subject Categories : Acoustics
      Miscellaneous Materials
      Aircraft


Distribution Statement : APPROVED FOR PUBLIC RELEASE