Numerical and experimental investigation of aeroacoustic damping characteristics of perforated orifices
Date of Issue2016-02-10
School of Mechanical and Aerospace Engineering
Acoustic liners perforated with thousands of millimeter-size circular oriﬁces are widely used on aero-engines as an eﬀective noise damper. To investigate and optimize the aeroacoustic damping behavior of these perforated liners, numerical simulations of in-duct oriﬁces are performed ﬁrst. For this, both two- and three-dimensional numerical models of acoustically excited ﬂow through perforated oriﬁces with diﬀerent geometric shapes are conducted in the time domain by using the lattice Boltzmann method. It is shown that vortex rings are formed when incident sound waves interact with and destabilize the shear layers formed at the oriﬁce rims, and the sound energy is converted into kinetic energy being dissipated by the surrounding air. Unlike frequency-domain simulations typically found in the literature, the damping behavior of the oriﬁces is quantiﬁed in the present work over a broad frequency range at a time by forcing an oscillating ﬂow with multiple tones. Good agreement is observed between numerical results with the ones obtained from theoretical models. Parametric study is then conducted. It is found that the damping performance depends on the mean ﬂow, the plate thickness, the oriﬁces’geometric shape and dimensions.