Acoustic resonance excitation and source mapping in co-axial piping systems with different junction edge geometries

Abstract

In this study, the excitation of acoustic resonance in a coaxial piping system consisting of two opposite pipe branches is experimentally investigated. A lumped element model is used to determine the complex acoustic source, enabling the prediction of resonance excitation under specific flow conditions. The model is validated by assessing the susceptibility of two opposite side branches to acoustic resonance excitation. The predicted acoustic resonance parameters show good agreement with experimental observations in terms of the Strouhal numbers and normalized acoustic pressure amplitudes across a range of flow velocities. Additionally, the effects of rounding and chamfering the edges of the branching junction on resonance excitation are explored. Results indicate that rounded edges produce higher acoustic pressure amplitudes compared to chamfered and sharp edges, with a significant increase in Strouhal numbers at resonance. Furthermore, increasing the rounding radius raises both the onset flow velocity and the lock-in region. The influence of flow development and acoustic radiation losses on the excitation mechanism is also investigated. Findings show that side branches with fully developed flow and reduced acoustic radiation losses to the main pipe are more prone to acoustic resonance excitation and resonate at higher Strouhal numbers. However, the predicted acoustic amplitude reaches a maximum once the upstream distance allows for full flow development over the branching junction.