CAA analysis of a Wing Section with Flap Side-Edges Based on Hybrid RANS-LES Computation

Based on hybrid RANS-LES computation of the turbulent flow around a double-flapped wing section, CAA (Computational Aero-Acoustics) analysis was conducted using the Curle, the Kirchhoff and the FW-H acoustic analogy methods. The focus was placed on the flow-induced noise due to the flap side-edges (FSE). It was shown that the FSE has triggered extensive unsteady vortex motions and being the most potent noise-generating source with significant pressure fluctuations on the side-edge surface. In the CAA analysis, two integral surfaces, defined by the iso-surface of vorticity magnitude, were verified when using the Kirchhoff and the FW-H methods. The Kirchhoff method is more sensitive to the location of the integral surface. The analysis using the Curle method indicates that the pressure fluctuations on the surface of the main wing and the first flap have made similar contributions to the far-field noise level, while the second flap contributes slightly less. The Kirchhoff and FW-H methods have predicted overall higher noise levels comparing to the Curle method. In the comparison, the result obtained with a stochastic method based on a RANS solution was also involved. The result has clearly demonstrated that, to capture the most potential noise generation in the presence of flap side edges, turbulence-resolving simulations should be incorporated in hybrid CFD/CAA analysis.