International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol: 11 No: 03 24 118403-7272 IJMME-IJENS © June 2011 IJENS I J E N S Abstract— Method of active flow control can be applied to reduce aerodynamic drag of the vehicle. It provides the possibility to modify locally the flow, to remove or delay the separation position or to reduce the development of the recirculation zone at the back as well as the separated swirling structures around the vehicle. In this study, a passenger van is modeled with a modified form of Ahmed's body by changing the orientation of the flow from its original form (modified/reversed Ahmed Body). This model is equipped with suction and blowing on the rear side to comprehensively examine the pressure field modifications that occur in order to modify the near wall flow toward reducing the aerodynamics drag. The computational simulation used is k-epsilon flow turbulence model. In this configuration, the front part of body was inclined at an angle of 35 ◦ with respect to the horizontal. The geometry is placed in a 3D-rectangular numerical domain with length, width and height equal to 8l, 2l and 2l, respectively. The suction and blowing velocities are set to 1 m/s, 5 m/s, 10 m/s and 15 m/s, respectively. The results show that aerodynamic drag reductions close to 15.83 % for suction and 14.38 % for blowing have been obtained. Index Terms— drag reduction, active flow control, suction, blowing, reversed Ahmed body. I. INTRODUCTION ccording to the conclusions of International Energy Agency in World Energy Outlook 2007, the gas emissions with greenhouse effect will increase close to 57% in 2030 with strong effects on the environment and the climate [1]. The human activities became main cause of the increase of the greenhouse gases effect and average global temperature. The activities included the transportation sector Manuscript received May 10, 2011. This work was supported by Incentive of Fundamental Research grant, The Ministry of Research and Technology Republic of Indonesia under contract no. RD-2011-0863 a Dr. Harinaldi is with the Department of Mechanical Engineering Faculty of Engineering University of Indonesia, Depok, Jawa Barat, 16424, Indonesia (Phone:+62-21-7270032;Fax:+62-21-7270033;e-mail:harinald@eng.ui.ac.id). b Prof. Budiarso is with the Department of Mechanical Engineering Faculty of Engineering University of Indonesia, Depok, Jawa Barat, 16424, Indonesia (Phone:+62-21-7270032;Fax:+62-21-7270033;e-mail:mftbd@eng.ui.ac.id). c Mr. Rustan Tarakka is a PhD student at the Department of Mechanical Engineering Faculty of Engineering University of Indonesia; e-mail: rustan_tarakka@yahoo.com d Mr. Sabar P. Simanungkalit is a Master degree student at the Department of Mechanical Engineering Faculty of Engineering University of Indonesia; e- mail: sp.simanungkalit@gmail.com where the growth number of automobile is rapidly increasing and make the fuel consumption increases as well. It tends to create harmful effects on the environment because it increases air pollution in the world. Based on these problems it has become a must for automobile industry in the world to immediately create an environmentally friendly automobiles and efficient in fuel consumption. Fuel consumption of automobile is related to its aerodynamics drag, and the magnitude of aerodynamics drag is highly influenced by separation flows around its shape. Meanwhile, the flow around a traveling automobile is complex and presents nonlinear interactions between different parts of the automobile so that many research institutions and industrial laboratories have been focusing their investigations automotive aerodynamics with numerical studies [2]. It is necessary to modify locally the flow, to remove or delay the separation position or to reduce the development of the recirculation zone at the back and of the separated swirling structures. This can be mainly obtained by controlling the flow near the wall with or without additional energy using active or passive devices [3]. Significant results can be obtained using simple techniques [4,5]. Many active control techniques which have been developed by focusing on local intervention in wall turbulence deal with steady blowing or suction [6,7,8]. A blowing devices installed in an ONERA D profile can shift or even prevent the flow separation to occur [9]. A local suction system located on the upper part of the rear window is capable of eliminating the rear window separation on simplified fastback car geometry. Aerodynamic drag reductions close to 17% have been obtained [10]. Other numerical works [11] using Lattice Boltzmann method to an Ahmed body model indicated some important parameters of active control to improve the aerodynamics performance of a vehicle. Most of previous numerical study in flow around automobile’s body used the geometry suggested by Ahmed [12] as shown in Fig. 1. Ahmed body allows reproducing flows phenomena around the vehicles and making a possibility to apply active control. However, to be practically implemented in controlling the flow separation in the automotive application the active control methods still need further comprehensive investigations to obtain some fundamental insights of the governing mechanism of separation control. Hence, the current investigation was a part of a long-term fundamental Computational Analysis of Active Flow Control to Reduce Aerodynamics Drag on a Van Model Harinaldi a , Budiarso b , Rustan Tarakka c and Sabar P. Simanungkalit d Department of Mechanical Engineering Faculty of Engineering University of Indonesia, Kampus UI-Depok, , Jawa Barat, 16424, Indonesia A