Manufacturing Process and Boundary Layer Influences on Perforate Liner Impedance

Abstract

This paper reports on the design and test of single layer perforate configurations. Results are presented assessing the influence of the manufacturing process on panel effective acoustic behaviour and the grazing flow influence on installed impedance, as measured using the in-situ technique. Impedance models are derived from the test data, based on both Mach number and skin friction velocity correlations, the latter following the approach of Kooi and Sarin. The study confirms the need for the combination of a well controlled perforate liner manufacturing process, plus accurate impedance models in order to ensure maximum performance may be achieved from perforate designs. Nomenclature