Aerodynamic and Aeroacoustic Analysis of a Harmonically Morphing Airfoil Using Dynamic Meshing

Chawki Abdessemed,Yufeng Yao,Abdessalem Bouferrouk

doi:10.3390/acoustics3010013

Chawki Abdessemed, Yufeng Yao + Show 1 more

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https://doi.org/10.3390/acoustics3010013

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Abstract

This work explores the aerodynamic and aeroacoustic responses of an airfoil fitted with a harmonically morphing Trailing Edge Flap (TEF). An unsteady parametrization method adapted for harmonic morphing is introduced, and then coupled with dynamic meshing to drive the morphing process. The turbulence characteristics are calculated using the hybrid Stress Blended Eddy Simulation (SBES) RANS-LES model. The far-field tonal noise is predicted using the Ffowcs-Williams and Hawkings (FW-H) acoustic analogy method with corrections to account for spanwise effects using a correlation length of half the airfoil chord. At various morphing frequencies and amplitudes, the 2D aeroacoustic tonal noise spectra are obtained for a NACA 0012 airfoil at a low angle of attack (AoA = 4°), a Reynolds number of 0.62 × 106, and a Mach number of 0.115, respectively, and the dominant tonal frequencies are predicted correctly. The aerodynamic coefficients of the un-morphed configuration show good agreement with published experimental and 3D LES data. For the harmonically morphing TEF case, results show that it is possible to achieve up to a 3% increase in aerodynamic efficiency (L/D). Furthermore, the morphing slightly shifts the predominant tonal peak to higher frequencies, possibly due to the morphing TEF causing a breakup of large-scale shed vortices into smaller, higher frequency turbulent eddies. It appears that larger morphing amplitudes induce higher sound pressure levels (SPLs), and that all the morphing cases induce the shift in the main tonal peak to a higher frequency, with a maximum 1.5 dB reduction in predicted SPL. The proposed dynamic meshing approach incorporating an SBES model provides a reasonable estimation of the NACA 0012 far-field tonal noise at an affordable computational cost. Thus, it can be used as an efficient numerical tool to predict the emitted far-field tonal noise from a morphing wing at the design stage.

Highlights

The phenomenal growth of the aviation industry with its associated environmental and noise pollution has motivated the European commission to set a vision for 2050 in its Flightpath 2050 project [1] to reduce the perceived noise by up to 65%, or the equivalent of a 15 dB reduction relative to the year 2000 levels
As the first step towards predicting and understanding the aerodynamic and noise aspects of harmonically morphing trailing edge flaps (TEF), this paper explores the capabilities of a hybrid RANS-Large Eddy Simulation (LES) approach
It is based on a modified unsteady parametrization method defining the TEF motion, and dynamic meshing tools for mesh deformation

Summary

Introduction

The phenomenal growth of the aviation industry with its associated environmental and noise pollution has motivated the European commission to set a vision for 2050 in its Flightpath 2050 project [1] to reduce the perceived noise by up to 65%, or the equivalent of a 15 dB reduction relative to the year 2000 levels. NASA developed aerodynamic surfaces that are highly flexible and could be optimized in-flight [2] Such concept proved to be an efficient technique to decrease airframe noise and to enhance lift and reduce drag, all so crucial in civil aviation transport. Airframe noise reductions attributed to morphing concepts are mainly due to the streamlining of the wing and the removal of gaps presented between some rigidly moving elements of the lifting surfaces such as flap side-edges, slotted slats, and trailing edge flaps (TEF) [3,4]

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