Aerodynamic and aeroacoustic evaluation of slat and slot separation control on a small-scale HAWT: A computational study

The global push toward clean energy has intensified the search for efficient, innovative technologies to harness renewable resources. Small-scale horizontal-axis wind turbines (HAWTs) offer a promising solution to meet growing urban energy demands with minimal environmental impact. This computational study investigates the aerodynamic and aeroacoustic effects of two passive flow separation control techniques, slat and slot, applied to the blades of a small-scale HAWT. Using the NREL S809 Phase II rotor as a benchmark, simulations are conducted using the steady Moving Reference Frame (MRF) and the unsteady Sliding Mesh Motion (SMM) approaches. The k-ω SST turbulence model is validated against experimental data for multiple inflow conditions. The results demonstrate that flow separation is significantly mitigated by both control methods, particularly at higher wind speeds and at specific locations along the blade span. Quantitatively, the slat and slot configurations yield power output increases of 8.74 % and 21.07 %, respectively, compared to the baseline case. However, aeroacoustic analysis reveals that the slot introduces a sound pressure level (SPL) increase of up to 20 dB near 1 kHz, while providing a more balanced performance in terms of noise and energy gain. These findings highlight the slot configuration as a particularly effective solution for enhancing aerodynamic efficiency, while the slat provides a more balanced aeroacoustic profile. The choice between them involves a trade-off between maximum power gain and noise-control requirements in small-scale wind energy systems.