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The University of Southampton
Engineering

Liner splices

Longitudinal acoustically “hard” strips or splices can be used to fasten acoustic linings in turbofan ducts. The presence of splices has been shown using analytical (and also numerical) methods to cause azimuthal mode scattering, which may reduce the overall sound attenuation. Longitudinal acoustically “hard” strips or splices can be used to fasten acoustic linings in turbofan ducts. The presence of splices has been shown using analytical (and also numerical) methods to cause azimuthal mode scattering, which may reduce the overall sound attenuation.

It has been shown that reducing the splice width reduces the scattered energy. As a result of this type of analysis, "splice-less" liners are now being designed and manufactured. 

Simulations of a spinning mode in a lined duct with and without splices are shown below.

 

 No splices

 

 

 

 

 

 

 

 

 

 

 

With splices

 

 

 

 

 

 

 

 

 

 

 

A simulation showing the effect of varying the splice width on the amplitudes of the scattered modes is shown below.

 

Transmitted mode amplitudes with a liner containing one splice of varying width

Related publications:

Tester, B.J., Powles, C.J., Baker, N.J. and Kempton, A.J. Scattering of sound by liner splices: A Kirchhoff model with numerical verification. AIAA Journal, 44(9), 2006, 2009-17.

McAlpine, A. and Wright, M.C.M. Acoustic scattering by a spliced turbofan inlet duct liner at supersonic fan speeds. Journal of Sound and Vibration, 292(3-5), 2006, 911-34.

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