Trailing edge serrations for noise control in axial-flow automotive cooling fans

This study investigated the use of trailing edge serrations to reduce the noise generated by axial-flow automotive cooling fans. Three different serration profiles (sinusoidal, rectangular, and triangular) were examined, with the profiles being extended radially along the entire blade length and truncated at half the blade length while keeping the dimensionless wave number k^∗ and wave amplitude 2h^∗ constant. The simulations employed a hybrid URANS-LES solver for the flow field and Ffowcs Williams-Hawkings analogy for the sound field, corresponding to the maximum volumetric flow rate and fan rotational speed. Acoustic pressure measurements were taken at multiple receivers upstream and downstream of the fan, and the overall sound pressure level was computed based on the results. Furthermore, the study also compared the aerodynamic performance of all serration types with the baseline fan, revealing that the baseline fan was relatively more efficient than their serrated counterparts. Despite the reduced efficiency, the trailing edge serrations offered significant noise reduction benefits of up to 10 dB, making them a promising solution for improving acoustic comfort in automotive cooling systems.