Numerical Simulation of Underhood Cooling Noise for Off-Highway Application

A mockup was designed to mimic a simple underhood cooling case with the fan commonly used in the off-highway applications. A wind tunnel test was performed first to make sure the mockup could reproduce a realistic mass flow rate and pressure drop typical for these applications. Afterwards, the noise from the mockup was measured in a semi-anechoic chamber using multiple microphones. Various installation configurations were tested such as tip clearance, upstream obstructions, and shrouds. The sound pressure level at multiple locations for the certain installation configurations was simulated and compared to the test data. The flow field was computed using a hybrid RANS/LES approach and the sound pressure level was predicted using the Ffowcs Williams and Hawkins model with a commercially available software. The result shows an excellent comparison between the test and the simulation both in tonal noise and broad band noise up to the frequency of interest for typical engineering applications.