Numerical Study of Noise Reduction via Flow Obstruction in Low-Speed Axial Fans

Low speed axial fans are widely used in industrial application, such as in HVAC and cooling systems, but their acoustic signature can significantly impact comfort and noise regulation compliance. Fan noise generally consists of broadband and tonal components. Tonal noise is often perceived as more annoying due to its distinct, periodic character, making it a critical target for mitigation strategies. Traditional noise reduction strategies often involve complex modifications to blade design or active control techniques, which can be costly or impractical. This thesis investigates an alternative numerical approach for reducing tonal noise at the Blade Passing Frequency via a flow obstruction placed upstream of the fan. The work aims to provide a framework for evaluating the potential of flow obstructions in mitigating tonal noise while maintaining fan efficiency, focusing on modeling the downstream velocity profile and integrating the obstruction effects into an existing analytical model. Validation is carried out through Lattice Boltzmann Method simulations. Preliminary evaluations of aerodynamic performance are also conducted. The proposed method offers the additional advantage of reduced computational cost compared to high-fidelity simulations, providing a practical tool for early-stage design assessments.