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

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.

Near Stall Unsteady Flow Responses to Morphing Flap Deflections

“…Diffusion-based smoothing was used in the present work because it is more robust when it comes to mesh quality preservation (as required for moving boundaries) compared with spring-based smoothing [21]. The exact setup in [16] was replicated using diffusion-based smoothing to deform the computational grid, and for this specific case with large deformation a limited patch of triangular cells was introduced near the TE (Figure 3) in order to use the remeshing feature included in ANSYS Fluent [21]. Readers are directed to [16,30] for in-depth details of the dynamic mesh setup.…”

“…, x FOR PEER REVIEW 6 of 19 deformation a limited patch of triangular cells was introduced near the TE (Figure 3) in order to use the remeshing feature included in ANSYS Fluent [21]. Readers are directed to [16,30] for in-depth details of the dynamic mesh setup.…”

“…Rezaeiha et al [27] demonstrated that 2.5D SBES is a superior approach to both URANS and scale-adaptive simulation (SAS). Finally, Abdessemed et al [16] conducted a comparative study between 2D SBES and 3D LES for the same configuration and Reynolds number (0.408 × 10 6 ), with the results showing that the 2D SBES approach was able to accurately capture the loads and flow features with a fraction of the numerical cost, which is sufficient for the current study to obtain trends and inform future works.…”

“…In a different experiment at a high Reynolds number of 1 million, Jodin et al [14] showed that a substantial reduction in flow instabilities could be obtained using a vibrating TEF, in addition to an increase in the aerodynamic efficiency, if the flap vibrations are set at optimal frequencies and amplitudes. The use of a harmonically morphing TEF was also explored numerically for both aerodynamic and aeroacoustic performance enhancements [15,16] at low AoAs. It was shown that up to a 3% increase in the aerodynamic efficiency could be obtained, together with a 1.5 dB reduction of tonal noise.…”

Meshing for Exhaust System Design on L12B Engine

“…Meshing is the process of retraining or discrete in a continuous fluid domain to be converted into a discrete computing domain. Meshing is the main requirement determining the success of CFD simulation [1][2][3][4][5].…”