Effect of bulk-reacting liners on sound wave propagation in annular variable area ducts

An analysis is presented for the effect of Y-HZ/zircon porous composites as a bulk-reacting liner on the sound wave propagation and attenuation in an annular lined variable area duct with flow. The sound propagation in the lining material is coupled with the wave propagation in the main duct, the analysis include the effect of main flow velocity in both the up and down-stream propagation. The results show that, the increase in porosity increases the attenuation, the increase in liner thickness and the resistivity increase the attenuation in the high frequency range but, decrease the attenuation in the low frequency range, the increase in temperature increases the attenuation specially in the down stream propagation. The use of Zircon porous Ceramics is very valuable in attenuation of noise emitted from the jet engine exhaust ducts as they have a good thermal and mechanical properties at high temperatures up to (1800 K) beside their good attenuation effect and their light weight.