Influence of Gurney Flap and Leading-Edge/Trailing-Edge Flaps on the Stall Characteristics and Aeroacoustic Performance of Airfoils
Abstract
1. Introduction
2. Numerical Simulation of Flow Around NACA0021 Using DDES
2.1. Computational Modeling and Mesh Generation
- .
2.2. Grid Independence Verification
2.3. Verification of the Accuracy of Simulation Results
2.4. Simulation Results of Airfoil Model with Gurney Flap Airfoil and Leading- and Trailing-Edge Flap Airfoils
3. Acoustic Noise Analysis
3.1. Noise Spectrum
3.2. Noise Mechanism Analysis of the Gurney Flap Airfoil
3.3. Noise Mechanism Analysis of the Leading-Edge and Trailing-Edge Flap Airfoil
4. Conclusions
- At an angle of attack of 20°, numerical simulations show that both the Gurney flap airfoil and the leading- and trailing-edge flap airfoil exhibit significant improvements in lift and drag compared to the baseline airfoil. The Gurney flap notably enhances lift with minimal change in drag, resulting in a substantial increase in lift-to-drag ratio. For the airfoil with leading- and trailing-edge flaps, both lift and drag increase considerably, but the lift-to-drag ratio also shows a moderate improvement. The surface pressure coefficient distributions further reveal that the installation of Gurney flaps and leading- and trailing-edge flaps leads to a marked increase in suction-side pressure, thereby contributing to the enhancement of lift.
- In terms of spatial radiation characteristics, compared to the baseline airfoil, the Gurney flap airfoil shows a slight reduction of 0.15 dB in overall sound pressure level (OASPL) at the trailing edge (0° azimuth) and a slight increase of 0.63 dB at the leading edge (180° azimuth), indicating minimal changes at these two positions. However, in the regions between 0 and 90° and 270 and 360° azimuth, the OASPL increases by more than 2.5 dB. For the airfoil equipped with leading- and trailing-edge flaps, the OASPL increases at most azimuthal angles, with a maximum rise of up to 11.8 dB. Nevertheless, in the vicinity of the leading edge, specifically within the 135–195° azimuth range, the maximum reduction in OASPL reaches approximately 4.1 dB. These results suggest that both types of flow control generally lead to increased noise across most azimuthal directions, with the leading- and trailing-edge flap configuration causing a more pronounced noise increase near the trailing edge. However, a noise reduction effect is observed near the leading edge for the airfoil with leading- and trailing-edge flaps, with a maximum noise reduction rate of 4.4%.
- At an azimuthal angle of 0°, within the low- to mid-frequency range (25–1250 Hz), the Gurney flap airfoil exhibits higher sound pressure levels than the baseline airfoil across most frequencies, with a maximum increase of 9.4 dB observed at 50 Hz. In the mid- to high-frequency range (1250–10,000 Hz), the Gurney flap airfoil shows higher sound pressure only at 10,000 Hz, where it exceeds the baseline by 0.85 dB; at all other frequencies, it exhibits lower sound pressure levels, with a maximum reduction of 14.7 dB at 2000 Hz. This indicates that near the trailing edge, the Gurney flap has a positive effect in suppressing noise in the mid- to high-frequency range. At an azimuthal angle of 180°, within the mid- to high-frequency range (400–3150 Hz), the baseline airfoil displays higher sound pressure levels compared to the airfoil with leading- and trailing-edge flaps, with a maximum increase of 8.19 dB at 1250 Hz. This suggests that near the leading edge, the combined leading- and trailing-edge flaps are effective in suppressing noise within the mid- to high-frequency range.
- The pressure fluctuations in the flow field and the surface sound pressure level (SPL) contours of the airfoil were analyzed to better understand the mechanisms by which the two flow control strategies influence noise generation. For the Gurney flap airfoil, the distribution range of peak pressure fluctuations near the trailing edge at 0° azimuth and near the leading edge at 180° azimuth is larger compared to the baseline airfoil. At the trailing edge, noise is mainly generated by the interaction between the airfoil surface and the airflow, constituting the primary source of noise. The presence of the Gurney flap leads to finer and more fragmented wake vortices, thereby reducing the noise contribution from wake vortex interactions within this frequency range. In contrast, for the airfoil equipped with combined leading- and trailing-edge flaps, pressure fluctuations near the leading edge at 180° azimuth are significantly lower than those of the baseline airfoil, resulting in reduced leading-edge noise. However, at the trailing edge, the noise level increases compared to the baseline, with the noise predominantly originating from wake vortex interactions, while the contribution from the interaction between the airfoil surface and the airflow is relatively minor.
- By applying two flow controls to the original airfoil, it can be seen that an increase in the airfoil lift-to-drag ratio is accompanied by an increase in noise generation. Since the Gurney flap airfoil enhances the lift resistance ratio much more than the leading- and trailing-edge flap airfoils in this flow condition, and its influence on the noise generation is smaller compared to the leading- and trailing-edge flap airfoils, it is an excellent flow control method for enhancing lift and controlling noise.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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EXP | 6 × 106 | 4 × 106 | 2 × 106 | |
Cl | 0.931 | 0.906 | 0.914 | 0.89 |
Δ | −2.76% | −1.86% | −4.61% | |
Cd | 1.517 | 1.467 | 1.473 | 1.436 |
Δ | −3.41% | −2.99% | −5.64% |
EXP | EADS-M | 400w | |
Cl | 0.931 | 0.889 | 0.914 |
Δ | −4.51% | −1.86% | |
Cd | 1.517 | 1.425 | 1.473 |
Δ | −6.06% | −2.99% |
EXP | CFD Plain | CFD Gurney | Enhancement Percentage | |
---|---|---|---|---|
Cl | 0.443 | 0.332 | 0.643 | 93.68% |
Cd | 0.285 | 0.252 | 0.253 | 0.39% |
Lift-to-Drag Ratio | 1.557 | 1.317 | 2.542 | 93.01% |
EXP | CFD Plain | CFD LEF&TEF | Enhancement Percentage | |
---|---|---|---|---|
Cl | 0.443 | 0.332 | 0.548 | 65.06% |
Cd | 0.285 | 0.252 | 0.346 | 37.30% |
Lift-to-Drag Ratio | 1.554 | 1.317 | 1.583 | 20.19% |
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Liu, Z.; Li, K.; Sun, X. Influence of Gurney Flap and Leading-Edge/Trailing-Edge Flaps on the Stall Characteristics and Aeroacoustic Performance of Airfoils. Fluids 2025, 10, 152. https://doi.org/10.3390/fluids10060152
Liu Z, Li K, Sun X. Influence of Gurney Flap and Leading-Edge/Trailing-Edge Flaps on the Stall Characteristics and Aeroacoustic Performance of Airfoils. Fluids. 2025; 10(6):152. https://doi.org/10.3390/fluids10060152
Chicago/Turabian StyleLiu, Zelin, Kaidi Li, and Xiaojing Sun. 2025. "Influence of Gurney Flap and Leading-Edge/Trailing-Edge Flaps on the Stall Characteristics and Aeroacoustic Performance of Airfoils" Fluids 10, no. 6: 152. https://doi.org/10.3390/fluids10060152
APA StyleLiu, Z., Li, K., & Sun, X. (2025). Influence of Gurney Flap and Leading-Edge/Trailing-Edge Flaps on the Stall Characteristics and Aeroacoustic Performance of Airfoils. Fluids, 10(6), 152. https://doi.org/10.3390/fluids10060152