Effect of aspect ratio on the recirculation region of 35° Ahmed body

ABSTRACT

This paper reports a numerical investigation of the effect of aspect ratio (AR) on the flow structure around the 35° Ahmed body. The AR is defined as the ratio of length to the height of the model. A total of five ARs are considered at a Reynolds number based on the height of the Ahmed body of 7.8  105. The flow governing equations are solved in the FLUENT solver using the SST K-Omega turbulence model.  It is found that the drag coefficient (Cd) slightly increases at the AR1 4.2%. As the aspect ratio increases, the drag coefficient decreases. The analysis reveals that early flow separation in the AR1 causes a reattachment at the rear slant end, which leads to an increase in drag. It also highlights that there exists a minimum aspect ratio beyond which the drag increases. and there is a limit in the increasing order beyond which the drag will begin to reduce. Further, it demonstrates that there is no change in the recirculation region and consequently drag coefficient is not a function of the recirculation region. Thence, a clear understanding of the effect of the length-based aspect ratio can help to optimize the length during design.

KEYWORDS:

• Aspect ratio based on length
• Ahmed body aerodynamics
• lift and drag of Ahmed body
• vortex generation around the bluff body
• effect of length
• vortex core

Nomenclature

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Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Naseeb Ahmed Siddiqui

Naseeb Ahmed Siddiqui is a Ph.D. student at Ontario Tech University in the Faculty of engineering and applied science. His research area is the nature-inspired drag reduction devices, Aerodynamics of the bluff bodies and wings, Experimental and Computational fluid dynamics.

Martin Agelin-Chaab

Martin Agelin-Chaab  is an Associate Professor at the Department of Mechanical and Manufacturing Engineering, Faculty of Engineering and Applied Science at Ontario Tech University. Bluff body/ground vehicle aerodynamics, Turbulent flows, and jets Vehicle, and battery thermal analyses Sustainable energy systems are his research area.