Reynolds-averaged Navier-Stokes simulations of two partial-span flap wing experiments

TLDR

The purpose of these tests was to accurately document the acoustic and aerodynamic characteristics associated with the principal airframe noise sources, including flap side‑edge noise. Structured RANS simulations of two partial‑span flap wing experiments were performed using multiple block‑structured grids, various turbulence models, and grid‑block interface methods to calibrate CFL3D and resolve flap‑side‑edge flow features not seen experimentally. Numerical results agree excellently with experimental measurements and flow visualization, resolving the flap‑edge flow field and substantiating the merger of two vortical structures, thereby enabling simplified airframe noise models.

Abstract

Structured Reynolds Averaged Navier-Stokes simulations of two partial-span flap wing experiments were performed. The high-lift aerodynamic and aeroacoustic wind-tunnel experiments were conducted at both the NASA Ames 7-by 10-Foot Wind Tunnel and at the NASA Langley Quiet Flow Facility. The purpose of these tests was to accurately document the acoustic and aerodynamic characteristics associated with the principle airframe noise sources, including flap side-edge noise. Specific measurements were taken that can be used to validate analytic and computational models of the noise sources and associated aerodynamic for configurations and conditions approximating flight for transport aircraft. The numerical results are used to both calibrate a widely used CFD code, CFL3D, and to obtain details of flap side-edge flow features not discernible from experimental observations. Both experimental set-ups were numerically modeled by using multiple block structured grids. Various turbulence models, grid block-interface interaction methods and grid topologies were implemented. Numerical results of both simulations are in excellent agreement with experimental measurements and flow visualization observations. The flow field in the flap-edge region was adequately resolved to discern some crucial information about the flow physics and to substantiate the merger of the two vortical structures. As a result of these investigations, airframe noise modelers have proposed various simplified models which use the results obtained from the steady-state computations as input.