Flow-induced sound generation in ducts containing flat plates: A numerical study

A duct containing a flat plate closely represents air-conditioning ducts in which air flow generates unwanted acoustic noise. This work studies the flow and acoustic fields in a duct of 50 × 50 ( m m ) rectangular cross-section containing a flat plate of 1 ( m m ) thickness, focusing on the conditions that lead to acoustic resonance. The computational procedure employs one-way coupling between a Large Eddy Simulation (LES) incompressible flow solver and an acoustic solver based on the Perturbed Convective Wave Equation (PCWE) model. The effects of plate length, number of plates, inflow Reynolds number (Re), and plate angle on the acoustic behaviour are investigated. The results show that changing the plate length alters both dominant resonance frequency and sound pressure levels, while varying the inflow velocity changes the sound pressure levels. Additionally, adjusting the plate angle broadens the dominant frequency towards lower values. Moreover, while by increasing number of plates, the flow turbulence intensifies and new modes arise, the sound pressure levels at dominant resonance frequency diminish.