On Predicting Aeroacoustic Performance of Ducts with Broadband Noise Source Models

A numerical method of predicting aeroacoustic performance of HVAC ducts is presented here. The method comprises of two steps. First, the steady state flow structure inside a duct is simulated using computational fluid dynamics (CFD). A k-epsilon based turbulence model is used. In the second step broadband noise source models are used to estimate the sound power generation within the duct. In particular, models estimating dipole and quadrupole sound source strengths are studied.

A baseline generic duct geometry was studied with 3 additional design variations. The loudness rankings of these three designs were determined numerically. Simultaneously, the sound generated by these three designs was measured on a flow bench with a microphone kept downstream of the duct outlet. The numerically predicted loudness rankings were compared with experimentally determined rankings and the two are found to be in agreement, thus validating the numerical method.