This study investigates into the challenging field of aeroacoustics research and focuses on how the Fowler-Williams-Hawkings (FW-H) model can be used to study sound in high-rise structures. Building on the reference paper “Numerical Simulation Study of Aerodynamic Noise in High-Rise Buildings [1]” this study looks at how aerodynamic forces and noise spread in cities and how they interact with each other. The FW-H model is an important part of aeroacoustics because it predicts the sound that will be made by swirling fluid motion and aerodynamic forces. We want to give you a full picture of how architectural design can affect and reduce aerodynamic noise by combining advanced numerical studies with the FW-H model. Not only does this study add to the field of urban acoustics, but it also helps builders and engineers make cities that are more sustainable and pleasant to live in.

• Reference [1]: Li, Zhengnong, and Jianan Li. “Numerical simulation study of aerodynamic noise in high-rise buildings.” Applied Sciences19 (2022): 9446.

Simulation Process

Three high-rise buildings are erected in the middle of a 3d rectangular domain. The geometry design is divided into blocks to generate a structured grid, using ANSYS ICEM software. A user-defined function (UDF) is written for the inlet boundary in which the wind velocity gradient is given in a way that boundary layer near the ground remains realistic. As the title suggests, FW-h acoustic model is adopted, supported by 4 receivers that can record sound.

Figure 1: Structured grid over buildings for aeroacoustics analysis – ANSYS ICEM

Post-processing

With a top speed of 31.12 m/s, the velocity contour shows an extensive flow field around the building. Because there are three separate building parts, there are several wake regions with low-speed zones (blue areas) and vortex shedding. These flow patterns are very important for making aerodynamic noise because when high-speed streams and slow-moving wake regions meet, they cause big changes in pressure and turbulence.

Figure 2: Velocity on 2D plane around the high-rise buildings for aeroacoustics analysis

The spectral study of pressure at receiver-1 tells us a lot about how the noise is made. According to the octave band analysis, the low frequency is the most important one. The sound pressure levels are greatest below 5 Hz, at about 44 dB. The main modes of vortex shedding are matched by this low-frequency dominance, which is common in wind-induced noise in big structures. As the frequency goes up, the sound pressure level drops quickly, hitting about 25 dB at higher frequencies (above 40 Hz). This spectral distribution fits with the fact that aerodynamic noise is broadband, meaning that its energy is spread out over a lot of different frequencies but is mostly in the lower bands. The in-depth frequency study backs up these results even more, showing that the loudest sounds (below 1 Hz) have a peak sound pressure level of almost 100 dB. It is clear that the sound pressure level drops quickly as the frequency goes up. In the 20–50 Hz range, levels drop to around 40–50 dB. This changing behavior with frequency fits with what you’d expect from flow-induced noise, where bigger, slower-moving swirls make the low-frequency parts stronger, and smaller-scale turbulence makes the high-frequency parts.

Figure 3: Sound pressure level & amplitude captured by receiver 1