Simulation study on aerodynamic noise characteristics in ventilation ducts with internal baffles

In this study, a parametric study on aerodynamic noise of a ventilation duct with an internal baffle is conducted based on Lighthill's acoustic analogy method. The variation regularities of far-field noise radiation under different flow velocities and baffle angles are explored. The results show that the aerodynamic noise is mainly dominated by low-frequency components under the working conditions. As the baffle angle and flow velocity increase, the overall noise level rises accordingly, while the noise spectral characteristics remain basically unchanged in most frequency ranges with only amplitude variations. Nevertheless, prominent noise peaks appear at specific frequency points under certain conditions, and such peaks become more pronounced with the decrease of baffle angle. To reveal the noise generation mechanism, a hybrid numerical method is adopted. Specifically, the wall pressure data on the duct inner wall and baffle surfaces are extracted from the computational fluid dynamics (CFD) software STAR-CCM+, which are then converted into dipole sound sources in Simcenter 3D to simulate the noise propagation inside and outside the duct. Internal acoustic field analysis demonstrates that the spectral peaks are mainly induced by Parker modes in the duct, and their frequency locations and amplitudes are closely related to baffle angle and flow velocity. Moreover, higher-order acoustic modes are also observed within the duct. This study clarifies the aerodynamic noise characteristics and generation mechanism of ducts with internal baffles under flow conditions, which provides an important basis for the subsequent noise reduction design.