Point vortex model for prediction of sound generated by a wing with flap interacting with a passing vortex

Area of Science:

• Fluid dynamics
• Aeroacoustics
• Computational physics

Background:

• Understanding the acoustic signature of airfoils is crucial for noise reduction in various applications.
• The interaction of fluid flow with structures, like wings with flaps, generates complex acoustic phenomena.
• Previous studies have focused on static or detached flaps, leaving the dynamic interaction with a movable flap less explored.

Purpose of the Study:

• To investigate the acoustic signature generated by a rigid wing with a movable flap interacting with a line vortex.
• To analyze the fluid-structure interaction and its effect on sound radiation.
• To determine the role of the flap's natural frequency in sound amplification or absorption.

Main Methods:

• Utilized a two-dimensional, low-Mach number flow simulation.
• Employed thin-airfoil methodology and the emended Brown and Michael equation for fluid-structure interaction analysis.
• Applied the Powell-Howe analogy to analyze far-field acoustic radiation.

Main Results:

• Incident vortex passage excites flap motion at the system's natural frequency.
• The acoustic signature is dominated by vortex sound from airfoil-vortex interactions and wake sound from flap motion.
• Direct flap motion has a minimal impact on total sound radiation.

Conclusions:

• The movable flap can act as a sound amplifier or absorber, contingent on the flap-fluid natural frequency.
• The study provides insights into the acoustic behavior of flapped airfoils in dynamic vortex interaction scenarios.
• This research complements existing knowledge on airfoil acoustics with static and detached flap configurations.