THE EFFECT OF WAVE PARAMETERS ON AERODYNAMIC COEFFICIENTS DURING WING-IN-GROUND EFFECT FLIGHT

Öz

In this study, the ground effect, which affects the aerodynamic performance of aircraft flying near wavy ground was investigated with time-dependent 2D Unsteady RANS-based Computational Fluid Dynamics (CFD) analyses. Analyses were conducted using a NACA 4412 airfoil under various wave amplitudes, wavelengths, and angles of attack. In the analyses, the airfoil was held stationary, and a sinusoidal moving ground model was applied underneath to simulate the periodic wave effect. The variation of lift, drag, and moment coefficient (CL, CD, Cm) values according to different wave positions was determined. It was determined that the highest CL occurred when approaching the wave crest and the lowest when approaching the trough. The effects of wave parameters, angles of attack, and proximity to the ground on the airfoil were analyzed. Results reveal that lift coefficient (CL) varies by 26.04 % over a wave period (from 0.962 to 1.250) for the most dynamic case (AOA=8°, h/c=0.4, λ/c=1, α/c=0.2). Maximum lift occurs at wave crests (CL=1.250), representing a 14.2% increase relative to time-averaged values, while minimum lift at wave troughs shows a 13% decrease. Ground clearance reduction from h/c=0.8 to h/c=0.4 amplifies fluctuations by 37%, while wavelength increase from λ/c=1 to λ/c=3 reduces variations by 58%.

Anahtar Kelimeler

• Wavy ground
• Lift
• Drag
• Wavelength
• Wave Amplitude
• Unsteady RANS

YER ETKİSİ ALTINDA UÇUŞTA DALGA PARAMETRELERİNİN AERODİNAMİK KATSAYILAR ÜZERİNDE ETKİSİ

Öz

Bu çalışmada, dalgalı zemine yakın uçan uçakların aerodinamik performansını etkileyen zemin etkisi, zamana bağlı 2D Kararsız RANS tabanlı Hesaplamalı Akışkanlar Dinamiği (CFD) analizleri ile incelenmiştir. Analizler, çeşitli dalga genlikleri, dalga boyları ve hücum açıları altında NACA 4412 kanat profili kullanılarak gerçekleştirilmiştir. Analizlerde, kanat profili sabit tutulmuş ve periyodik dalga etkisini simüle etmek için altına sinüzoidal hareketli zemin modeli uygulanmıştır. Farklı dalga konumlarına göre kaldırma, sürtünme ve moment katsayısı (CL, CD, Cm) değerlerinin değişimi belirlenmiştir. En yüksek CL 'nin dalga tepesine yaklaşırken, en düşük CL 'nin ise dalga çukuruna yaklaşırken meydana geldiği belirlenmiştir. Dalga parametrelerinin, hücum açılarının ve zemine yakınlığın kanat profili üzerindeki etkileri analiz edilmiştir. Sonuçlar, en dinamik durumda (AOA=8°, h/c=0,4, λ/c=1, α/c=0,2) kaldırma katsayısının (CL) dalga periyodu boyunca %26,04 oranında değiştiğini (0,962'den 1,250'ye) ortaya koymaktadır. En yüksek kaldırma kuvveti dalga tepelerinde (CL=1,250) meydana gelir ve bu da zaman ortalamalı değerlere göre %14,2'lik bir artışı temsil ederken, dalga çukurlarında minimum kaldırma kuvveti %13'lük bir azalma göstermektedir. Yerden yüksekliğin h/c=0,8'den h/c=0,4'e düşmesi dalgalanmaları %37 oranında artırırken, dalga boyunun λ/c=1'den λ/c=3'e artması varyasyonları %58 oranında azaltmaktadır.

Anahtar Kelimeler

• Dalgalı zemin
• Kaldırma kuvveti
• Sürükleme kuvveti
• Dalga boyu
• Dalga Genliği
• Kararsız RANS

Kaynakça

1. References
2. Rozhdestvensky K V. (2006). Wing-in-ground effect vehicles. Vol. 42, Progress in Aerospace Sciences. 211–283. Nebylov A, Nebylov V, Fabre P. (2015). WIG-Craft flight control above the waved sea. In IFAC-Papers OnLine. 102–107.
3. Ockfen AE, Matveev KI. (2009). Aerodynamic characteristics of NACA 4412 airfoil section with flap in extreme ground effect. International Journal of Naval Architecture and Ocean Engineering; 1(1): 1–12. Hu H, Ma D. (2020) Airfoil aerodynamics in proximity to wavy ground for a wide range of angles of attack. Applied Sciences (Switzerland); 10(19).
4. Liu X, Ma D, Yang M, Guo Y, Hu H. (2021). Numerical study on airfoil aerodynamics in proximity to wavy water surface for various amplitude. Applied Sciences (Switzerland); 11(9).
5. Liang H, Zong Z, Zou L. (2013). Nonlinear lifting theory for unsteady WIG in proximity to incident water waves. Part 1: Two-dimensional. Applied Ocean Research; 43:99–111.
6. Jung JH, Yoon HS, Chun HH, Hung PA, Elsamni OA. (2012). Mean flow characteristics of two-dimensional wings in the ground effect. International Journal of Naval Architecture and Ocean Engineering; 4(2): 151–161.
7. He W, Guan Y, Theofilis V, Li LKB. (2019). Stability of low-Reynolds-number separated flow around an airfoil near a wavy ground. AIAA Journal; 57(1): 29–34.
8. Matdaud Z, Zhahir A, Pua'At AA, Hassan A, Ahmad MT. (2019). Stabilizing Attitude Control for Mobility of Wing in Ground (WIG) Craft -A Review. In: IOP Conference Series: Materials Science and Engineering. Institute of Physics Publishing.

9. Su Y, Li D, Zhao S. (2024). Lift augmentation of a circulation control airfoil in proximity to water waves. In: Journal of Physics: Conference Series. Institute of Physics.
10. Qu Q, Lu Z, Liu P, Agarwal RK. (2014). Numerical study of aerodynamics of a wing-in-ground-effect craft. Journal of Aircraft; 51(3): 913– 924.
11. Tofa MM, Maimun A, Ahmed YM, Jamei S, Priyanto A, Rahimuddin. (2014). Experimental investigation of a wing-in-ground effect craft. The Scientific World Journal: 7.
12. Zaheer Z, Reby Roy KE, Nair GS, Ragipathi V, Niranjan U V. (2019). CFD analysis of the performance of different airfoils in the ground effect. In: Journal of Physics: Conference Series. Institute of Physics Publishing.
13. Smuts EM, Sayers AT. (2011). CFD Study of a Wing in Close Proximity to a Flat and Wavy Ground Plane. Journal of the South African Institution of Mechanical Engineering. vol 27.
14. Lee T, Lin G. (2022). Review of experimental investigations of wings in ground effect at low Reynolds numbers. Frontiers in Aerospace Engineering; 1.
15. Firooz A, Gadami M. (2006). Turbulence Flow for NACA 4412 in Unbounded Flow and Ground Effect with Different Turbulence Models and Two Ground Conditions: Fixed and Moving Ground Conditions. Int. Conference on Boundary and Interior Layers, University of Sistan and Baloochestan, Zahean, Iran.
16. Kaya, M. N. (2025). Numerical investigation of transonic shock wave characteristics on supercritical airfoils under various flow conditions. Konya Journal of Engineering Sciences, 13(4), 1252-1263.
17. Çelik, Y. (2025). Task-specific airfoil design for fixed-wing UAVs in high-climb reconnaissance missions: A CST and XFOIL-based approach. Turkish Journal of Nature and Science, 14(4), 66-84.
18. Kaya, M. N. (2025). Numerical simulation of laminar non-Newtonian blood flow under varying Reynolds numbers and geometric parameters using OpenFOAM. Bulletin of Biomathematics, 3(2), 150-163.