Master of science

4.3 Aerodynamic Analysis of LMV with Add-on Spoiler

. . It is common in real world that a SUV or a crossover has a downward spoiler. Generally, for a SUV or a crossover, the angle of its rear spoiler will be downward at 1 -30 degree. The best angle studied for a generic SUV is around 15 degree [28]. Therefore, the tested spoiler angle here is determined to be 15 degree to verify its typical performance. The dimension of the spoiler is 60mm in width, 18.5mm in thickness and the length matches the vehicle body as showed in Figure 4.5,. The simulation results of velocity magnitude and total pressure are showed in Figure 4.6 and Figure 4.7 that the spoiler reduces the wake region which reduces the drag. While it is reducing the wake region, the LMV generates less lift at the same time because of slope of its hatchback that is also called lift-back. The simulation generates the results indicating that the drag coefficient is equal to 0.43 and that the lift coefficient is equal to -0.067. With this add-on device, both drag and lift are reduced. As we discussed in Chapter 3, the spoiler is different from the rear wing. The main function of a spoiler is to reduce drag but not aim to generate downward force. From data of the simulation, it shows that the spoiler successfully reduced the drag without significantly affecting the lift. With add-on spoiler, the vehicle maintains its stability and improves its fuel economy. With a reduction in drag coefficient of 0.044 and a reduction in lift coefficient of 0.007, which equals about to 6.6 pounds weigh increase, the fuel improvement is, estimated about 0.87 mpg.

Figure 4.6 LMV with Add-on Spoiler

Figure 4.7 Velocity Magnitude of LMV with Spoiler

Figure 4.8 Total Pressure of LMV with Spoiler