Passive drag reduction of square back road vehicles

• Main Authors: Altaf, Alaman, Omar, Ashraf Ali, Asrar, Waqar
• Format: Article
• Language: English; English
• Published: Elsevier Ltd. 2014
• Subjects: TL1 Motor vehicles
• Online Access: http://irep.iium.edu.my/38911/4/1-s2.0-S0167610514001640-main.pdf; http://irep.iium.edu.my/38911/7/38911_Passive%20drag%20reduction%20of%20square%20back%20road%20vehicles.SCOPUS.pdf; http://irep.iium.edu.my/38911/; http://www.elsevier.com/locate/jweia

Bluff body vehicles such as trucks and buses do not have a streamlined shapes and hence have high drag which can be reduced to make great savings in operational cost. While rectangular flaps have been widely studied as both passive add-ons and in active drag reducing systems for bluff bodies, changing the basic geometry of the flap has not been explored in literature. In this work, a baseline drag value is obtained for a simplified MAN TGX series truck in a CFD software, and the drag reduction of a proposed elliptically shaped flap is compared to aerodynamically equivalent rectangular flaps. The optimal mounting angle for both flaps is found to be 501. A parametric study of changing the ellipse semi-major axis is carried out to find the optimal length for drag reduction. A maximum drag reduction of 11.1% is achieved using an elliptical flap with 0.12 m semi-major axis; compared to 6.37% for a length equivalent rectangular flap, and 6.84% for a surface area equivalent rectangular flap. Results of the pressure distribution and velocity flow behind the rear of the truck are also given and analyzed.