Master of science

4.4 Aerodynamic Analysis of LMV with Add-on Vortex Generator (VG)

In this simulation, we apply the vortex generator to LMV to verify its function for LMV. The VG is installed 100 mm in front of the rear end as shown in Figure 4.8. Figure 4.9 and Figure 4.10 present the pressure distributions of LMV with Vortex Generator installed. The CFD yields the drag coefficient of 0.504 and the lift coefficient of -0.056, indicating that it has no significant lift difference compared to the simulation results from LMV without any add-on devices. For this drag reduction, it is estimated about 0.65 mpg decrease in fuel economy. As we have reviewed in previous chapter that the vortex generator is sensitive to the flow velocity. In addition, the big size of the VG may generate drag by itself when air flow is passing over it. Inappropriate installation of VG might even result in more drags. As we have seen in the Figure 4.10, the absolute pressure value is higher in the front of the VG that is generating drag. However, the function of the VG is to delay the flow separation and this might reduce the same amount of drag force as the VG generates itself. Better VG installation position and choice of its geometry might be able to improve its performance.

Figure 4.9 LMV with Vortex Generator

Figure 4.10 Dynamic Pressure of LMV with Vortex Generator