Effects of Geometric Parameters of Perforated Diffuser on Sound Pressure Level Sourced By Airflow

Abstract

This study investigates the aeroacoustic behaviors of a square truncated perforated diffuser under airflow, commonly used in Air Handling Units (AHUs). The design parameters are fundamentally taken into account to unveil the aeroacoustic performance of the diffuser. Initially, unsteady-state Computational Fluid Dynamics (CFD) simulations are conducted based on models that accurately represent the fluid domain of the chamber with the perforated diffuser in the ANSYS Fluent environment. Subsequently, the Ffowcs Williams and Hawkings (FW-H) method integrated into the software is employed to acquire time-dependent signals from microphones placed in three different locations within a perforated diffuser chamber. Finally, the results are converted to a frequency range of 0-1000 Hz using the Fast Fourier Transform (FFT) method, and the SPL values are obtained. The results show that the microphone location is crucially important to determine SPL and the porosity reduction from 0.55 to 0.35 can reduce SPL by approximately 30-40 dB. Variations in wall thickness of the diffuser fluctuated between 5-10 dB at each frequency value.