Surface curvature effects on the tonal noise performance of a low Reynolds number aerofoil

Abstract

This paper presents wind tunnel experiments to illustrate the effects of surface curvature on the aeroacoustic performance of airfoil E387. For the first time, surface curvature effects are considered in an investigation of the airfoil's self-noise. To distinguish the effects of surface curvature, the CIRCLE method is applied to the airfoil E387 to remove slope-of-curvature discontinuities and the redesigned airfoil is denoted A7. Anechoic wind tunnel tests were performed with E387 and A7 at three low Reynolds numbers to investigate aeroacoustic performance by measuring airfoil self-noise at different angles of attack (AoA) and spatial positions. At 2 • and 4 • AoA, A7 presents a tone with a reduced amplitude compared with E387 due to its improved slope-of-curvature distribution. It is concluded that improving surface curvature distribution improves airfoil aeroacoustic performance.

Low Reynolds number proprotor aerodynamic performance improvement using the continuous surface curvature design approach

“…It was found to yield a delay in the burst of the leading edge separation bubble and thus a delay in the stall of thin aerofoil at high angle-of-attack (AOA). This was confirmed by RANS and Large Eddy Simulations (LES) carried using Ansys ( 2 , 3 ) and our in-house code CgLES ( 5 ) . It was also further validated using detailed wind tunnel tests ( 3 ) .…”

“…The variations of the thrust and power coefficients with the TSR are given in Fig 10, where for the model, the c l &c d variations were based on Re C =10 5 . For consistency the experimental propeller results were re-adjusted for the definitions of the thrust and power coefficients, and tip speed ratio as commonly used for rotor aerodynamics and as are used in this study.…”

“…It resulted in the new profiles QM13F and A7, replacing NACA0012 and E387, respectively. Redesigning the original spiky trailing edges of the NACA0012 and E387 to rounded trailing edges actually led to reduction in the production costs of the metal profiles ( 3 , 5 ) .…”

“…1, showing the lift and drag coefficients c l and c d variations as taken from Shen et al ( 2 , 3 ) . At low AOA, the CIRCLE design approach was experimentally and computationally found to reduce the laminar separation bubble (LSB) over the profile’s upper surface and thus mildly reduce the drag and significantly reduce the tonal trailing edge noise by up to 10 dB ( 3 , 5 ) . The noise reduction occurred due a decrease in the LSB size which resulted in suppressing its interaction with the trailing edge and its flapping.…”

Effect of passive flow control on the aerodynamic performance, entropy generation and aeroacoustic noise of axial turbines for wave energy extractor

“…The flow generated sound in normal operation (unstalled) was decreased up to 3 dB by optimal backward/ forward blade skew. The vast majority of the researchers and investigations focused on the aerodynamic noise prediction for wind turbine [76][77][78][79][80][81] and around an airfoil [82][83][84][85][86][87][88]. However, no study until now study the aeroacoustic noise prediction or reduction of Wells turbine at stall and near-stall conditions under oscillating flow conditions, even, the only research group for the aerodynamic noise prediction of Wells turbine mentioned be in [74,75], assumed that Wells turbine work under unidirectional flow with steady state condition.…”