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This paper presents an iterative super-resolution technique based on time-reversal (TR) to simultaneously improve the localization accuracy and enhance the focal-resolution of airfoil trailing-edge (TE) noise source. Experiments were conducted in an anechoic wind tunnel for low Mach number flow whereby the acoustic pressure was recorded using two line arrays of microphones located above and below a NACA0012 airfoil test-model. TR simulations were carried out in different tonal and broadband frequency range without and with rigid-wall modeling of the scattering surfaces which include the experimental facility and the airfoil. Without scatterer modeling, the TR simulation yields deviation of the source location from the TE; the dipole location was predicted in the wake. When the self-scattering due to airfoil was taken into account, the scattered field source exhibited a cardioid directivity. However, large side lobes presents difficulty in readily identifying the true location of the scattered source at low- and high-frequency range. To remove ambiguity in identifying the scattered source location, the Point-Time-Reversal-Sponge-Layer (PTRSL) damping technique is implemented (whilst simultaneously modeling the airfoil) which is centered at an optimal location obtained through iterations. The technique is based on the principle that implementation of the PTRSL in the source vicinity increases the sound pressure level (SPL) at focal points of the enhanced source map. For a given frequency range, a set of simulations were carried out to identify the optimal PTRSL center which yields maximum SPL at the focal point. It was shown that the iterative PTRSL technique yields the scattered source location between the mid-chord and TE region, thereby improving the localization accuracy, in particular, for the low-frequency broadband and high-frequency secondary tonal noise. Furthermore, this technique was shown to produce approximately lambda/4-lambda/5 transverse resolution of the scattered source, thereby yielding a highly enhanced focal-resolution.
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