Direct noise simulation of an installed Controlled Diffusion airfoil at high angle-of-attack

Direct Numerical Simulations (DNS) of the compressible flow over a Controlled Diffusion (CD) airfoil are conducted at a high angle-of-attack of 15°. To obtain far-field noise predictions, the compressible DNS results are coupled with both solid and porous Ffowcs Williams and Hawkings acoustic analogy. The mean installation effects associated with open-jet anechoic wind tunnel conditions are included in these computations. A large flow separation with the shedding of large coherent structures is observed in the front part of the airfoil, followed by a reattachment at mid-chord, and a second flow detachment downstream. Similar to the work previously conducted at a geometrical angle of attack of 8°, three noise sources have been found: the flow separation and reattachment; the interaction between the attached turbulent flow at the trailing edge; and a secondary instability in the near wake. • Jet confinement effects producing modifications in the boundary-layer extension. • Three noise sources: laminar separation bubble, trailing edge, and near-wake. • Leading edge laminar separation bubble dominant noise source at all frequencies. • Leading edge laminar separation bubble modifies the directivity pattern downstream.