G - Physics – 01 – N
Patent
G - Physics
01
N
349/35
G01N 29/04 (2006.01) G01H 15/00 (2006.01)
Patent
CA 1276282
ABSTRACT Apparatus and method for determining the steady state flow resistance of face sheets on fully assembled acoustic duct liners. Resistance is measured by subjecting the liner to a sinusoidal acoustic pressure field at the face sheet surface. The pressure field is applied through a cylindrical waveguide and is measured by a pressure transducer flush mounted on the inside of the waveguide near the liner face. A second pressure measurement, obtained by a similar transducer posi- tioned further from the face, is combined with the first measurement to calculate the acoustic resistance for the excit- ation frequency. If the excitation frequency coincides with the resonant frequency of the liner configuration, then no significant pressure exists on the back surface of the liner face sheet. For this condition the root mean square (rms) pressure measured at the face sheet is equated to the static pressure drop used to obtain the steady state flow resistance. The rms velocity of the oscillating pressure wave is calculated from the ratio of rms pressure to resistance. A repetition of the procedure for several magnitudes of dynamic pressure permits the development of a curve which describes the non- linear characteristics of resistance with changes in velocity. this curve may be equated to a similar curve obtained using steady state flow resistance measurements of the liner in its partially assembled state without a backing surface.
542909
Gow Joseph P.
Noe Arcas
Parente Charles A.
Gow Joseph P.
Grumman Aerospace Corporation
Mcfadden Fincham
Parente Charles A.
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