Numerical study of active flow control in a toroidal propeller configuration
This study numerically investigates the effect of low-momentum blowing applied to a toroidal propeller on aerodynamic performance and aeroacoustic characteristics. A Delayed Detached Eddy Simulation (DDES) approach coupled with the Ffowcs–Williams and Hawkings (FW–H) acoustic analogy is employed to resolve unsteady flow structures and predict far-field noise signatures. Two configurations are examined at 3000 revolutions per minute (RPM): a baseline propeller and one equipped with active flow control (AFC). The results show that the introduction of AFC produces negligible changes in thrust, torque, and figure of merit (FM), indicating that equivalent aerodynamic performance is maintained. In contrast, noticeable acoustic benefits are achieved. Significant reductions in primary tonal noise and overall sound pressure level (OASPL) are observed along the propeller axis direction, with a maximum tonal reduction of approximately 6 dB and an OASPL decrease of up to 1.8 dB. Flow-field analysis using Q-criterion iso-surfaces and z-vorticity contours reveals that blowing weakens coherent vortex structures near the upper surface of the back blades around 0.75 R . The weakened vortical activity reduces unsteady surface pressure fluctuations, thereby attenuating dipole-type acoustic sources responsible for dominant axial radiation.