Numerical and experimental investigation of aeroacoustic damping characteristics of perforated orifices

• Main Author: Ji, Chenzhen
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Theses and Dissertations
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering::Aeronautical engineering
• Online Access: http://hdl.handle.net/10356/65968
• Institution: Nanyang Technological University

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.