  Extremum seeking control (ESC) and its slope seeking generalization are
applied in a high-fidelity flow simulation framework for reduction of acoustic
noise generated by a NACA0012 airfoil. Two Reynolds numbers are studied for
which different noise generation mechanisms are excited. For a low Reynolds
number flow, the scattering of vortex shedding at the airfoil trailing edge
produces tonal noise while, for a moderate Reynolds number case, boundary layer
instabilities scatter at the trailing edge leading to noise emission at
multiple tones superimposed on a broadband hump. Different control setups are
investigated and they are configured to either find an optimal steady actuator
intensity or an optimal position for a blowing/suction device. Implementation
details are discussed regarding the control modules and design of digital
filters.
