# Experimental Study on the Effect of Porous Media on the Aerodynamic Performance of Airfoils

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Experimental Scheme

#### 2.1. Wind Tunnel Test System and Experimental Model

^{−7}mm

^{2}, 1.31 × 10

^{−7}mm

^{2}, and 1.24 × 10

^{−8}mm

^{2}, respectively, with 98% porosity in all cases. Images of the porous media are shown in Figure 3. The three selected porous media had large pore density spans and considerable permeability changes; therefore, we could obtain the general control rule through our experiment.

#### 2.2. Experimental Equipment and Test Methods

#### 2.3. Ω Vortex Identification Method

## 3. Aerodynamic Measurement Results and Discussion

#### 3.1. Aerodynamic Force Results

#### 3.2. Pressure Distribution Results

## 4. Flow-Field Results and Discussion

#### 4.1. Time-Averaged Flow Field

#### 4.1.1. Time-Averaged Velocity Field

#### 4.1.2. Time-Averaged Shear Stress Field

#### 4.2. Unsteady Flow Field

#### 4.3. DMD Mode Analysis

#### 4.3.1. Mode Distribution

#### 4.3.2. Vortex–Mode Energy

#### 4.3.3. Conjugate Mode of the Vorticity Field

## 5. Conclusions

- (1)
- Only the porous media with the appropriate pore density (20 PPI) could significantly improve the aerodynamic performance of the airfoil. If the pore density of the porous media is too small, the aerodynamic performance of the airfoil will be seriously damaged in the whole range of the angle of attack. If the pore density is too large, the porous media may act like a spoiler, increasing the viscous effect, and the aerodynamic power of the airfoil will be reduced under the condition of a small angle of attack;
- (2)
- Porous media (20 PPI) mainly reduce the drag by considerably reducing the airfoil surface’s frictional resistance while the pressure resistance increases. It also can weaken the wall shear stress.
- (3)
- Porous media (20 PPI) can destroy the vortex structure, breaking a large-scale vortex with low-frequency into a high-frequency granular vortex, inhibit the amplitude of vortex fluctuation, effectively weaken the energy of different modes of the vortex, accelerate the vortex evolution process, and thus improve the airfoil’s aerodynamic performance.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

- Gad-el-hak, M. Modern developments in flow control. Appl. Mech. Rev.
**1996**, 49, 365–379. [Google Scholar] [CrossRef] - Kral, L.D. Active Flow Control Technology. ASME Fluids Eng. Div. Newsl.
**2000**, 1–28. [Google Scholar] - Liu, R.-B.; Wei, W.-T.; Wan, H.-P.; Lin, Q.; Li, F.; Tang, K. Experimental study on airfoil flow separation control via an air-supplement plasma synthetic jet. Adv. Aerodyn.
**2022**, 4, 32. [Google Scholar] [CrossRef] - Koca, K.; Genç, M.S.; Bayır, E.; Soğuksu, F.K. Experimental study of the wind turbine airfoil with the local flexibility at different locations for more energy output. Energy
**2022**, 239, 121887. [Google Scholar] [CrossRef] - Shao, S.; Guo, Z.; Hou, Z.; Jia, G.; Zhang, L.; Gao, X. Effects of Coanda jet direction on the aerodynamics and flow physics of the swept circulation control wing. Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng.
**2022**, 236, 2633–2654. [Google Scholar] [CrossRef] - Xu, F. Numerical Simulation of Fluid Structure Interaction Vibration and Flow Control of Structures; Harbin Institute of Technology: Harbin, China, 2009. [Google Scholar]
- Jaworski, J.W. Thrust and Aerodynamic Forces from an Oscillating Leading Edge Flap. AIAA J.
**2012**, 50, 2928–2931. [Google Scholar] [CrossRef] - De Tavernier, D.; Ferreira, C.; Viré, A.; LeBlanc, B.; Bernardy, S. Controlling dynamic stall using vortex generators on a wind turbine airfoil. Renew. Energy
**2021**, 172, 1194–1211. [Google Scholar] [CrossRef] - Jeong, J.S.; Bong, S.W.; Lee, S.W. An efficient winglet coverage for aeroengine turbine blade flat tip and its loss map. Energy
**2022**, 260, 125153. [Google Scholar] [CrossRef] - Walsh, M.; Weinstein, L. Drag and heat transfer on surfaces with small longitudinal fins. AIAA Pap.
**1978**, 78–1161. [Google Scholar] - Chen, L. The Discussion of Slip Phenomenon and Drag Reduction in Rough Micro-Channels; Huazhong University of Science and Technology: Wuhan, China, 2012. [Google Scholar]
- Wang, X.; Fan, Z.; Tang, Z.; Jiang, N. Drag reduction and hairpin packets of the turbulent boundary layer over the superhydrophobic-riblets surface. J. Hydrodyn.
**2021**, 33, 621–635. [Google Scholar] [CrossRef] - Huynh, D.P.; Huang, Y.; McKeon, B.J. Experiments and modeling of a compliant wall response to a turbulent boundary layer with dynamic roughness forcing. Fluids
**2021**, 6, 173. [Google Scholar] [CrossRef] - Bachmann, T.; Blazek, S.; Erlinghagen, T.; Baumgartner, W.; Wagner, H. Barn Owl Flight in “Nature-Inspired Fluid Mechanics”; Springer: Berlin/Heidelberg, Germany, 2012; pp. 101–117. [Google Scholar]
- Fedorov, A. Transition and stability of high-speed boundary layers. Annu. Rev. Fluid Mech.
**2011**, 43, 79–95. [Google Scholar] [CrossRef] - Venkataraman, D.; Bottaro, A. Numerical modeling of flow control on a symmetric airfoil via a porous, compliant coating. Phys. Fluids
**2012**, 24, 093601. [Google Scholar] [CrossRef] [Green Version] - Klausmann, K.; Ruck, B. Drag reduction of circular cylinders by porous coating on the leeward side. J. Fluid Mech.
**2017**, 813, 382–411. [Google Scholar] [CrossRef] - Joshi, S.N.; Gujarathi, Y.S. A review on active and passive flow control techniques. Int. J. Recent Technol. Mech. Electr. Eng.
**2016**, 4, 1–6. [Google Scholar] - Li, Q.; Pan, M.; Zhou, Q.; Dong, Y. Turbulent drag modification in open channel flow over an anisotropic porous wall. Phys. Fluids
**2020**, 32, 015117. [Google Scholar] [CrossRef] - Liu, H.; Chen, N.; Liu, Y.; Hu, Z. Review of porous media using in flow control and aerodynamic noise reduction. Acta Aeronaut. Astronaut. Sin.
**2023**, 44, 027923. [Google Scholar] - Mößner, M.; Radespiel, R. Flow simulations over porous media–Comparisons with experiments. Comput. Fluids
**2017**, 154, 358–370. [Google Scholar] [CrossRef] - Aldheeb, M.; Asrar, W.; Sulaeman, E.; Omar, A.A. Aerodynamics of porous airfoils and wings. Acta Mech.
**2018**, 229, 3915–3933. [Google Scholar] [CrossRef] - Tamaro, S. Numerical and Experimental Study of Airfoils with Porous Trailing Edge; Technische Universiteit Delft: Delft, The Netherlands, 2019. [Google Scholar]
- Tamaro, S.; Zamponi, R.; Ragni, D.; Teruna, C.; Schram, C. Experimental investigation of turbulent coherent structures interacting with a porous airfoil. Exp. Fluids
**2021**, 62, 1–18. [Google Scholar] [CrossRef] - Du, H.; Zhang, Q.; Li, Q.; Kong, W.; Yang, L. Drag reduction in cylindrical wake flow using porous material. Phys. Fluids
**2022**, 34, 045102. [Google Scholar] [CrossRef] - Du, H.; Li, Q.; Zhang, Q.; Zhang, W.; Yang, L. Experimental study on drag reduction of the turbulent boundary layer via porous media under nonzero pressure gradient. Phys. Fluids
**2022**, 34, 025110. [Google Scholar] [CrossRef] - Liu, C.Q.; Wang, Y.Q.; Yang, Y.; Duan, Z.W. New omega vortex identification method. Sci. China Phys. Mech. Astron.
**2016**, 59, 684711. [Google Scholar] [CrossRef] - Liu, C.; Gao, Y.; Dong, X.; Wang, Y.; Liu, J.; Zhang, Y.; Cai, X. Third generation of vortex identification methods: Omega and Liutex/Rortex based systems. J. Hydrodyn.
**2019**, 31, 205–233. [Google Scholar] [CrossRef] - Schmid, P.J. Application of the dynamic mode decomposition to experimental data. Exp. Fluids
**2011**, 50, 1123–1130. [Google Scholar] [CrossRef] - Schmid, P.J. Dynamic mode decomposition of numerical and experimental data. J. Fluid Mech.
**2010**, 656, 5–28. [Google Scholar] [CrossRef] [Green Version] - Krake, T.; Klötzl, D.; Eberhardt, B.; Weiskopf, D. Constrained Dynamic Mode Decomposition. IEEE Trans. Vis. Comput. Graph.
**2022**, 29, 182–192. [Google Scholar] [CrossRef]

Number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Suction side | x/c | 0.01 | 0.02 | 0.035 | 0.055 | 0.07 | 0.1 | 0.15 | 0.25 | 0.35 | 0.45 | 0.6 | 0.7 | 0.8 | 0.9 |

z/L | 0.5002 | 0.5004 | 0.5006 | 0.501 | 0.5012 | 0.5018 | 0.5027 | 0.5045 | 0.5062 | 0.508 | 0.5107 | 0.5227 | 0.5245 | 0.5263 | |

Pressure side | x/c | 0.015 | 0.04 | 0.08 | 0.12 | 0.3 | 0.4 | 0.5 | 0.65 | 0.75 | 0.85 | / | / | / | / |

z/L | 0.5003 | 0.5007 | 0.5014 | 0.5021 | 0.5034 | 0.5071 | 0.5089 | 0.5116 | 0.5234 | 0.5252 |

Mode Type | Airfoil Laid with Porous Media | Smooth Airfoil |
---|---|---|

Quasi-static | 1st | 1st |

Drifting | 4th | 2nd |

7th | 7th | |

12th | 10th | |

15th | 13th | |

/ | 14th | |

/ | 15th | |

Conjugate | 2nd and 3rd | 3rd and 4th |

5th and 6th | 5th and 6th | |

8th and 9th | 8th and 9th | |

10th and11th | 11th and 12th | |

13th and 14th | / |

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Kong, W.; Dong, H.; Wu, J.; Zhao, Y.; Jin, Z.
Experimental Study on the Effect of Porous Media on the Aerodynamic Performance of Airfoils. *Aerospace* **2023**, *10*, 25.
https://doi.org/10.3390/aerospace10010025

**AMA Style**

Kong W, Dong H, Wu J, Zhao Y, Jin Z.
Experimental Study on the Effect of Porous Media on the Aerodynamic Performance of Airfoils. *Aerospace*. 2023; 10(1):25.
https://doi.org/10.3390/aerospace10010025

**Chicago/Turabian Style**

Kong, Wenjie, Hao Dong, Jie Wu, Yidi Zhao, and Zhou Jin.
2023. "Experimental Study on the Effect of Porous Media on the Aerodynamic Performance of Airfoils" *Aerospace* 10, no. 1: 25.
https://doi.org/10.3390/aerospace10010025