Açık devre rüzgar tünelinde daralma konisi uzunluğunun optimizasyonu

Abstract

Bu çalışmada Literatürdeki çalışmalar çoğunlukla daralma konisinin eğriliğine odaklanırken, daralma uzunluğunun akış özellikleri üzerindeki etkisine ilişkin çalışmalar azdır. Çalışma, duvar kesme gerilme faktörünü birlikte dikkate alarak daralma konisinin çıkış bölümünde düzgün akış sağlayan daralma konisinin optimum uzunluğunu ortaya çıkarmayı amaçlamaktadır. Giriş hidrolik yarıçapının uzunluğuna bağlı olarak, farklı uzunlukta dört daralma konisi tasarlanmıştır. Tasarlanan geometriler için sayısal analiz yapılarak statik basınç ve hız dağılımları elde edilmiştir. Giriş hidrolik yarıçapının 2, 3 ve 3,5 katı daralma konisi uzunluğu ile tasarlanan rüzgar tünelinde de benzer bir akış patterni elde edildiği bulunmuştur. Bununla birlikte, daha uzun bir daralma eğrisi, akış bozukluklarını ve türbülansı en aza indirir ve bu, akış düzgünlüğüne yardımcı olur, oysa sınır tabakası büyümesi nedeniyle duvardaki kesme gerilmesi daha kalın sınır tabakası ile sonuçlanır. Bu nedenle, duvar kesme ve akış homojenliğinin birlikte etkisi göz önüne alındığında giriş hidrolik yarıçapının (kare daralma konisi) 2 katı daralma konisi uzunluğu ile yapılandırılmış rüzgar tünelinin en iyi seçim olduğu sonucuna varılmıştır.

Keywords

• Daralma konisi uzunluğu
• rüzgar tüneli
• nozul tasarımı
• düzün akış
• HAD.

Optimization of contraction cone length in an open-circuit wind tunnel

Abstract

The studies in the literature mostly focus on the curvature of the contraction cone, while research regarding the impact of contraction length on flow characteristics is limited. This study aims to determine the optimal length of the contraction cone, which ensures uniform flow at the outlet section, considering the wall shear factor. Four contraction cones of varying lengths were designed based on the hydraulic radius of the inlet. Numerical analysis was conducted to obtain static pressure and velocity distributions for the designed geometries. It was observed that wind tunnels designed with contraction cone lengths 2, 3, and 3.5 times the inlet hydraulic radius exhibited similar flow patterns. However, a longer contraction curve minimizes flow disturbances and turbulence, thereby enhancing flow uniformity and steadiness, while thicker boundary layers result from increased wall shears due to boundary layer growth. Consequently, it was concluded that a wind tunnel configured with a contraction cone length of 2 times the inlet hydraulic radius (square contraction cone) is the optimal choice, considering the combined effects of wall shear and flow uniformity.

Keywords

• Contraction cone length
• wind tunnel
• nozzle design
• flow uniformity
• CFD.

References

1. Witoszynski, C., Votraege aus dem gebiet der hydro- und aerodynamik, aus Stroemungstechnisches Messwesen bei S.G. Popow, VEB Verlag Technik Berlin, (1960).
2. Li, H., Chen, C., Liu, B., & Zhang, L., Flow quality analysis of contraction section and test section of low-speed wind tunnel based on CFD numerical simulation. Journal of Physics: Conference Series, vol. 1176, no. 5, p. 052064. IOP Publishing, (2019).
3. Morel, T. Design of two-dimensional wind tunnel contractions. ASME Journal of Fluids Engineering, vol. 99, pp. 371-378, (1977).
4. Bell, J. H., and Mehta, R. D. Contraction Design for Small Low Speed Wind Tunnels. NASA Contractor Rep. No. NASA-CR-177488, (1988).
5. Zanoun, E. S. Flow characteristics in low-speed wind tunnel contractions: Simulation and testing. Alexandria engineering journal, vol. 57, no. 4, , pp. 2265-2277, (2018).
6. Lastra, M. R. et al. Novel design and experimental validation of a contraction nozzle for aerodynamic measurements in a subsonic wind tunnel. Journal of Wind Engineering and Industrial Aerodynamics, vol. 118, pp. 35-43, (2013).
7. Ahmed, D. E., & Eljack, E. M. Optimization of model wind-tunnel contraction using CFD. International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, (2014).
8. Hoghooghi, H., Ahmadabadi, M. N., & Manshadi, M. D. Optimization of a subsonic wind tunnel nozzle with low contraction ratio via ball-spine inverse design method. Journal of mechanical science and technology, vol. 30, no. 5, pp. 2059-2067, (2016).

9. Rouse, H. Cavitation-free inlets and contractions (Electrical analogy facilitates design problem). Mech. Engng., vol. 71, pp. 213-416, (1949).
10. Sargison, J. E., Walker, G. J., & Rossi, R. Design and calibration of a wind tunnel with a two dimensional contraction., 15th Australasian Fluid Mechanics Conference, The University of Sydney, Sydney, Australia, (2004).
11. Barlow, J. B., Rae, W. H., & Pope, A. Low-speed wind tunnel testing. John Wiley & Sons, (1999).
12. Doolan, C. J. Numerical evaluation of contemporary low-speed wind tunnel contraction designs., J. Fluids Eng. (2007).
13. Ramaeshan, S., Ramaswamy, M.A. A rational method to choose optimum design for two dimensional contractions. ASME Journal of Fluids Engineering, vol. 124, pp. 544-546, (2002).
14. Arifuzzaman, M., & Mashud, M. Design construction and performance test of a low cost subsonic wind tunnel. IOSR Journal of Engineering, vol. 2, no. 10, pp. 83-92, (2012).
15. Mikhail, M. N. Optimum design of wind tunnel contractions. AIAA journal, vol. 17, no. 5, pp. 471-477, (1979).
16. Fang, F. M., Chen, J. C., & Hong, Y. T. Experimental and analytical evaluation of flow in a square-to-square wind tunnel contraction. Journal of Wind Engineering and Industrial Aerodynamics, vol. 89, no. 3-4,pp. 247-262, (2001).
17. Liu, J. S. Numerical Simulation and Optimization of Small low-speed Wind Tunnel Contraction flow. Applied Mechanics and Materials, vol. 733, pp. 595-598. Trans Tech Publications Ltd., (2015).
18. Callan, J., & Marusic, I. Effects of changing aspect ratio through a wind-tunnel contraction. AIAA journal, vol. 39, no. 9, pp. 1800-1803, (2001).
19. Mikel, Russell, ed. Wind Tunnels: Models, Aerodynamics and Applications. Clanrye International, (2015).
20. Javed, K., & Ali, M., Design & Construction of subsonic wind Tunnel focusing on two-dimensional contraction cone profile using sixth order polynomial., Scientific Cooperations International Workshops on Engineering Branches,(2014).
21. Passmann, M., Reinker, F., Hasselmann, K., aus der Wiesche, S., & Joos, F., Development and Design of a Two-Stage Contraction Zone and Test Section of an Organic Rankine Cycle Wind Tunnel. In Turbo Expo: Power for Land, Sea, and Air (Vol. 49743, p. V003T25A006). American Society of Mechanical Engineers, (2016).
22. Lakshman, R., and Ranjan Basak. Analysis of transformed fifth order polynomial curve for the contraction of wind tunnel by using OpenFOAM. IOP conference series: materials science and engineering. Vol. 377. No. 1. (2018).
23. Ismail, J., et al. Optimization Design of Open Circuit Wind Tunnel Suction Type. Int. J. Mech. Mechatronics Eng 17.06 121. (2017).
24. Abdelhamed, A. S., Y. El-S. Yassen, and M. M. ElSakka. Design optimization of three dimensional geometry of wind tunnel contraction. Ain Shams Engineering Journal. 6,1. 281-288. (2015).
25. Hasselmann, Karsten, et al. Numerical optimization of a piece-wise conical contraction zone of a high-pressure wind tunnel. American Society of Mechanical Engineers, Vol. 57212. (2015).
26. Bradshaw, P., Pankhurst, R. C., The design of low-speed wind tunnels. Progress in Aerospace Sciences, 5, 1-69, (1964).
27. John, Johanis, İsmail.İ., Pane E. Computational fluid dynamics simulation of the turbulence models in the tested section on wind tunnel. Ain Shams Engineering Journal 11.4 1201-1209. (2020).