Computational Aeroacoustic Modeling of Open Fan and Comparison of Predicted and Experimental Noise Fields

Modern high-speed turbo-machinery such as compressors and gas turbines can generate high level airborne noise from their fans/impellers. Here, the noise source locations and radiation characteristics of an open fan are predicted by using a Computational Aeroacoustic (CAA) model of the fan and compared to the experimental results obtained by using a Nearfield Acoustical Holography (NAH) method. The CAA model is built by using a commercial software package, ANSYS Fluent. In this model, the acoustic source data is extracted from a transient Computational Fluid Dynamic (CFD) analysis based on an unsteady k-I turbulence model. The NAH method is applied to sound pressure data measured by using an 8×8 microphone array to visualize the three-dimensional sound pressure fields. In addition, twelve reference microphones are used to decompose twelve incoherent partial sound pressure fields from the measured data. The CAA-predicted sound fields indicate that the fan noise sources consist of a combination of monopoles at the first blade passing frequency and its higher harmonics. The CAA model can be used to predict the sound pressure fields, radiated from the open fan, which agree well with the measured results in a wide frequency span.