Ceiling Fan Sound Generation: FW-H Vs. Wave Equation

Description

This project investigates noise generation from a ceiling fan in a room using ANSYS Fluent, comparing two distinct acoustic modeling approaches: the Ffowcs Williams and Hawkings (FW-H) integral method and a method based directly on the wave equation. The room is a 3D square domain measuring 4 m × 3 m × 4 m, with the fan centered in the room at a height of 2.7 m. Two square openings serve as inlet and outlet, with wind entering at 3 m/s. The geometry is built in Design Modeler and meshed in ANSYS Meshing, with 720,783 cells for the FW-H case and 534,016 cells for the wave equation case; given the inherently time-dependent nature of noise generation, both cases are run transient.

Methodology

In the first configuration, the fan is set rotating at 240 rpm using the Mesh Motion method, and noise is predicted using the FW-H integral method, with several receiver points placed at different locations in the room to sample the resulting sound field. In the second configuration, the fan is held fixed while wind continues to blow through the room at 3 m/s, and the noise generated purely from the wind colliding with the stationary fan blades is captured instead through a method based on the wave equation, isolating that collision-driven noise mechanism from the rotational one modeled in the first case.

Analysis

The results include 2D and 3D contours and plots of room pressure, temperature, and velocity, along with sound pressure and amplitude plots at the defined receiver points, generated in CFD Post. Temperature and velocity fields are shown as 3D contours throughout the room, while acoustic quantities are reported both on the fan surfaces and throughout the surrounding room environment. Comparing the two methods highlights how the fan's rotation versus the wind's direct impact on a stationary fan each contribute to the overall noise generated, giving two complementary perspectives on the same acoustic problem.