Abstract
Flow separation is expected to have the effect of increasing aerodynamic drag due to decreased pressure distribution at the rear of the vehicle. The faster the flow separation occurs, the lower the pressure distribution is in the area, thereby reducing vehicle performance. Therefore, flow modification is needed with expected effects on the separation delay and the reduction in wake and vortex formation. This modification can be done through the application of suction active control in the separation area. The research is intended to analyze the effect of suction active control on flow characteristics, pressure distribution and aerodynamic drag on vehicle models with suction velocity variations. The test model used is an Ahmed model modified by changing the orientation of the flow. The study used a numerical computational approach with a standard k-epsilon turbulence model at 19.4 m/s upstream velocity. Results revealed that the use of flow active control was able to reduce wake and vortex formation through separation delay and to increase the minimum pressure coefficient by 73% on the model with Usc<sub>2</sub> suction velocity of 0.5 m/s, gaining the highest drag coefficient reduction of 10.897% in the same model.
Highlights
Flow separation is a condition where flow passing through the surface of an object which no longer adheres to the object’s surface
The results showed the use of suction active control could eliminate flow separation and produce reduction in aerodynamic drag close to 17%
This is in line with the results obtained on the flow pattern characteristics and the increase in the pressure coefficient which shows that the model with the Usc2 suction velocity is the model that produces the smallest wake and vortex as shown in figure 9 and the highest increase in the minimum pressure coefficient as shown in table 7. These results are in line with research conducted by Tarakka et al [23] which found that the use of active controls on vehicle models is capable in reducing aerodynamic drag
Summary
Flow separation is a condition where flow passing through the surface of an object which no longer adheres to the object’s surface. Rearward suction is caused by large pressure differences between the front and the vacuum area that occurs at rear parts of the vehicle [7]. This affects the vehicle's performance due to the effects of aerodynamic drag. The results showed the use of active controls can increase the average pressure on all parts of the rear wall of the vehicle model and reduce aerodynamic drag by 9.4%. The results showed the application of suction active control placed on the back side of the vehicle model was effective to reduce the drag coefficient by 9%.
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