Bu çalışmada 25° ve 35°’lik arka eğim açısına sahip Ahmed gövdesinin arka eğimli yüzeyinin hücum kenarı üzerine dikdörtgen kanatlar eklenmiş ve bu geometrik model kullanılarak üç boyutlu, türbülanslı, daimî, sıkıştırılamaz akış için sayısal çözümler yapılmıştır. Tek, iki ve üç kanat olmak üzere üç farklı konfigürasyon göz önüne alınmıştır. Sayısal çözümler ticari hesaplamalı akışkanlar dinamiği çözücüsü ANSYS Fluent kullanılarak yapılmıştır. Sayısal modelin doğrulanması amacıyla, daha önce yapılmış bir deneysel çalışmanın sonuçları referans alınarak farklı türbülans modeli ve duvar fonksiyonu kombinasyonları ile sayısal çözümler yapılmıştır. Buna göre %8.8’lik hata ile k-epsilon Realizable türbülans modeli ve Menter-Lechner duvar fonksiyonu kombinasyonunun deneysel sonuçlara en yakın sonucu verdiği görülmüştür. Sayısal çözüm sonuçları, en iyi performansın kanatsız modele göre sürükleme katsayısında 2.3% oranında düşüşün sağlandığı, arka eğim açısı 25° olan üç kanatlı Ahmed modeli için elde edildiğini göstermiştir. Sürükleme katsayısı düşürme mekanizmalarının, arka yüzeyin hücum kenarı üzerinde bir emiş hattı oluşmasına ve ters yönlü olduğu halde akımın arka yüzeye tutunmasına bağlı olduğu tespit edilmiştir. Buna karşılık, arka eğim açısı 35° olan kanatlı Ahmed modeli için ise sürükleme katsayısında herhangi bir azalma görülmemiştir.
Byrne, C. E. I. (1999). Aerodynamics of Road Vehicles, 4th edition. Edited by WH. Hucho. SAE International, Warrendale, PA, USA. Materials Park, OH 44073-0002, USA 1998. 918 pp. Illustrated. 78. The Aeronautical Journal, 103(1026), 398-398.
McCallen, R., Salari, K., Ortega, J., Castellucci, P., Browand, F., Hammache, M., ... & Pointer, D. (2004, June). DOE's effort to reduce truck aerodynamic drag-joint experiments and computations lead to smart design. In 34th AIAA Fluid Dynamics Conference and Exhibit (p. 2249).
Ahmed, S. R., Ramm, G., & Faltin, G. (1984). Some salient features of the time-averaged ground vehicle wake. SAE Transactions, 473-503.
Siddiqui, N. A., & Chaab, M. A. (2020). A Simple Passive Device for the Drag Reduction of an Ahmed Body. Journal of Applied Fluid Mechanics, 14(1).
Delassaux, F., Mortazavi, I., Itam, E., Herbert, V., & Ribes, C. (2021). Sensitivity analysis of hybrid methods for the flow around the ahmed body with application to passive control with rounded edges. Computers & Fluids, 214, 104757.
Hanfeng, W., Yu, Z., Chao, Z., & Xuhui, H. (2016). Aerodynamic drag reduction of an Ahmed body based on deflectors. Journal of Wind Engineering and Industrial Aerodynamics, 148, 34-44.
McNally, J. W., Alvi, F. S., Mazellier, N., & Kourta, A. (2015). Active flow control on an ahmed body-an experimental study. In 53rd AIAA aerospace sciences meeting (p. 0825).
Tsai, C. H., Fu, L. M., Tai, C. H., Huang, Y. L., & Leong, J. C. (2009). Computational aero-acoustic analysis of a passenger car with a rear spoiler. Applied Mathematical Modelling, 33(9), 3661-3673.
Kurec, K., Remer, M., & Piechna, J. (2019). The influence of different aerodynamic setups on enhancing a sports car's braking. International Journal of Mechanical Sciences, 164, 105140.
Han, M. W., Rodrigue, H., Cho, S., Song, S. H., Wang, W., Chu, W. S., & Ahn, S. H. (2016). Woven type smart soft composite for soft morphing car spoiler. Composites Part B: Engineering, 86, 285-298.
Yuan, C. S., Mansor, S., & Abdullah, M. A. (2017). Effect of spoiler angle on the aerodynamic performance of hatchback model. Int. J. Appl. Eng. Res, 12(22), 12927-12933.
Altaf, A., Omar, A. A., & Asrar, W. (2014). Passive drag reduction of square back road vehicles. Journal of Wind Engineering and Industrial Aerodynamics, 134, 30-43.
Huminic, A., Huminic, G., & Soica, A. (2012). Study of aerodynamics for a simplified car model with the underbody shaped as a Venturi nozzle. International Journal of Vehicle Design, 58(1), 15-32.
Mohammadikalakoo, B., Schito, P., & Mani, M. (2020). Passive flow control on Ahmed body by rear linking tunnels. Journal of Wind Engineering and Industrial Aerodynamics, 205, 104330.
Buscariolo, F. F., Assi, G. R., & Sherwin, S. J. (2021). Computational study on an Ahmed Body equipped with simplified underbody diffuser. Journal of Wind Engineering and Industrial Aerodynamics, 209, 104411.
Kashyap, V., Arora, B. B., Bhattacharjee, S., & Mittal, P. (2019). Aerodynamic Effect of Aspect Ratio of Spherical Depressions on the Bonnet of Hatchback Cars (No. 2019-01-5096). SAE Technical Paper.
Shadmani, S., Mojtaba, M., Mojtaba Mousavi Nainiyan, S., Mirzaei, M., Ghasemiasl, R., & Pouryoussefi, S. G. (2018). Experimental investigation of flow control over an Ahmed body using DBD plasma actuator. Journal of Applied Fluid Mechanics, 11(5), 1267-1276.
Bayındırlı, C., Çelik, M., & Demiralp, M. (2018). Bir otobüs modeli etrafındaki akış yapısının CFD yöntemi ile incelenmesi ve sürükleme kuvvetinin pasif akış kontrol yöntemi ile iyileştirilmesi. Politeknik Dergisi, 21(4), 785-795.
Zafer, B., & Haskaraman, F. (2017). Önden ve yanal rüzgâr şartı altında Ahmed cisminin sayısal incelenmesi. Journal of the Faculty of Engineering & Architecture of Gazi University, 32(1).
Bayındırlı, C., & Çelik, M. Bir Taşıta Etki Eden Aerodinamik Direnç Kuvvetinin Bagaj Üstü Spoiler ile İyileştirilmesi. Afyon Kocatepe Üniversitesi Fen ve Mühendislik Bilimleri Dergisi, 19(2), 470-479.
Beaudoin, J. F., & Aider, J. L. (2008). Drag and lift reduction of a 3D bluff body using flaps. Experiments in fluids, 44(4), 491-501.
Le Good, G. M., & Garry, K. P. (2004). On the use of reference models in automotive aerodynamics.
Cengel, Y. A. (2010). Fluid mechanics. Tata McGraw-Hill Education
Numerical Investigation of Aerodynamic Properties of Ahmed Body for Different Rear Slanted Surface Configurations
The present study investigates aerodynamic characteristics of the Ahmed Body numerically, in case of that small rectangular flaps are attached to the leading edge of the rear slanted surface with a rear tilt angle of 25° and 35°. Numerical calculations have been conducted for three-dimensional, turbulent, steady, incompressible flow. Three different flap configurations have been considered: single flap, two flaps and three flaps. The commercial computational fluid dynamics solver ANSYS Fluent is used for the computations. To validate the numerical model, numerical solutions have been conducted with different combinations of turbulence model and wall functions, considering the values of drag coefficient obtained in a previous experimental work which studied slanted surface with flaps attached. Accordingly, k-epsilon Realizable turbulence model with Menter-Lechner wall function estimates the drag coefficient with an error of 8.8%. Results of the numerical calculations have shown that the best performance is obtained for the Ahmed model with 25° rear slant angle with three flaps mounted on the leading edge of the rear slanted surface, which provides a reduction in drag coefficient by 2.3%, compared to the model without flaps. Mechanisms for drag reduction are found to rely on generating a suction line along the leading edge of the rear slanted surface, which provides attached flow, although it is reversed. As for the 35° Ahmed model with flaps, on the other hand, no decrease in the drag coefficient is observed.
Byrne, C. E. I. (1999). Aerodynamics of Road Vehicles, 4th edition. Edited by WH. Hucho. SAE International, Warrendale, PA, USA. Materials Park, OH 44073-0002, USA 1998. 918 pp. Illustrated. 78. The Aeronautical Journal, 103(1026), 398-398.
McCallen, R., Salari, K., Ortega, J., Castellucci, P., Browand, F., Hammache, M., ... & Pointer, D. (2004, June). DOE's effort to reduce truck aerodynamic drag-joint experiments and computations lead to smart design. In 34th AIAA Fluid Dynamics Conference and Exhibit (p. 2249).
Ahmed, S. R., Ramm, G., & Faltin, G. (1984). Some salient features of the time-averaged ground vehicle wake. SAE Transactions, 473-503.
Siddiqui, N. A., & Chaab, M. A. (2020). A Simple Passive Device for the Drag Reduction of an Ahmed Body. Journal of Applied Fluid Mechanics, 14(1).
Delassaux, F., Mortazavi, I., Itam, E., Herbert, V., & Ribes, C. (2021). Sensitivity analysis of hybrid methods for the flow around the ahmed body with application to passive control with rounded edges. Computers & Fluids, 214, 104757.
Hanfeng, W., Yu, Z., Chao, Z., & Xuhui, H. (2016). Aerodynamic drag reduction of an Ahmed body based on deflectors. Journal of Wind Engineering and Industrial Aerodynamics, 148, 34-44.
McNally, J. W., Alvi, F. S., Mazellier, N., & Kourta, A. (2015). Active flow control on an ahmed body-an experimental study. In 53rd AIAA aerospace sciences meeting (p. 0825).
Tsai, C. H., Fu, L. M., Tai, C. H., Huang, Y. L., & Leong, J. C. (2009). Computational aero-acoustic analysis of a passenger car with a rear spoiler. Applied Mathematical Modelling, 33(9), 3661-3673.
Kurec, K., Remer, M., & Piechna, J. (2019). The influence of different aerodynamic setups on enhancing a sports car's braking. International Journal of Mechanical Sciences, 164, 105140.
Han, M. W., Rodrigue, H., Cho, S., Song, S. H., Wang, W., Chu, W. S., & Ahn, S. H. (2016). Woven type smart soft composite for soft morphing car spoiler. Composites Part B: Engineering, 86, 285-298.
Yuan, C. S., Mansor, S., & Abdullah, M. A. (2017). Effect of spoiler angle on the aerodynamic performance of hatchback model. Int. J. Appl. Eng. Res, 12(22), 12927-12933.
Altaf, A., Omar, A. A., & Asrar, W. (2014). Passive drag reduction of square back road vehicles. Journal of Wind Engineering and Industrial Aerodynamics, 134, 30-43.
Huminic, A., Huminic, G., & Soica, A. (2012). Study of aerodynamics for a simplified car model with the underbody shaped as a Venturi nozzle. International Journal of Vehicle Design, 58(1), 15-32.
Mohammadikalakoo, B., Schito, P., & Mani, M. (2020). Passive flow control on Ahmed body by rear linking tunnels. Journal of Wind Engineering and Industrial Aerodynamics, 205, 104330.
Buscariolo, F. F., Assi, G. R., & Sherwin, S. J. (2021). Computational study on an Ahmed Body equipped with simplified underbody diffuser. Journal of Wind Engineering and Industrial Aerodynamics, 209, 104411.
Kashyap, V., Arora, B. B., Bhattacharjee, S., & Mittal, P. (2019). Aerodynamic Effect of Aspect Ratio of Spherical Depressions on the Bonnet of Hatchback Cars (No. 2019-01-5096). SAE Technical Paper.
Shadmani, S., Mojtaba, M., Mojtaba Mousavi Nainiyan, S., Mirzaei, M., Ghasemiasl, R., & Pouryoussefi, S. G. (2018). Experimental investigation of flow control over an Ahmed body using DBD plasma actuator. Journal of Applied Fluid Mechanics, 11(5), 1267-1276.
Bayındırlı, C., Çelik, M., & Demiralp, M. (2018). Bir otobüs modeli etrafındaki akış yapısının CFD yöntemi ile incelenmesi ve sürükleme kuvvetinin pasif akış kontrol yöntemi ile iyileştirilmesi. Politeknik Dergisi, 21(4), 785-795.
Zafer, B., & Haskaraman, F. (2017). Önden ve yanal rüzgâr şartı altında Ahmed cisminin sayısal incelenmesi. Journal of the Faculty of Engineering & Architecture of Gazi University, 32(1).
Bayındırlı, C., & Çelik, M. Bir Taşıta Etki Eden Aerodinamik Direnç Kuvvetinin Bagaj Üstü Spoiler ile İyileştirilmesi. Afyon Kocatepe Üniversitesi Fen ve Mühendislik Bilimleri Dergisi, 19(2), 470-479.
Beaudoin, J. F., & Aider, J. L. (2008). Drag and lift reduction of a 3D bluff body using flaps. Experiments in fluids, 44(4), 491-501.
Le Good, G. M., & Garry, K. P. (2004). On the use of reference models in automotive aerodynamics.
Cengel, Y. A. (2010). Fluid mechanics. Tata McGraw-Hill Education
Kamacı, C., & Kaya, K. (2021). Numerical Investigation of Aerodynamic Properties of Ahmed Body for Different Rear Slanted Surface Configurations. Avrupa Bilim Ve Teknoloji Dergisi(28), 469-475. https://doi.org/10.31590/ejosat.1005846