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

• Published in: Australian journal of mechanical engineering 2023-03, Vol.21 (2), p.368-383
• Main Authors: Siddiqui, Naseeb Ahmed, Agelin-Chaab, Martin
• Format: Article
• Language: English
• Subjects: Ahmed body aerodynamics; Aspect ratio based on length; effect of length; lift and drag of Ahmed body; vortex core; vortex generation around the bluff body
• ISSN: 1448-4846; 2204-2253
• DOI: 10.1080/14484846.2020.1842307

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.