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Methodology Results and discussion 2016/7/13 1 Methodology Results and discussion For all the cases, the pressure coefficients in front of the bumper and 00the windscreen were positive, but that associated to the roof was always 00negative. there are more positive pressure coefficients on the upper wing of the 00spoiler for case 4 than other cases as shown in Fig. 5d. 2016/7/13 2 Methodology Results and discussion Fig. 6 shows the comparison of the drag and 00lift coefficients for the six cases studied. it is important to point out that only the 00spoiler for case 4 produced a negative lift 00coefficient. This implies that, among the 00design considered, the spoiler design 00number 4 produces the greatest vertical 00stability but that without a spoiler yields the 00worst. 2016/7/13 3 Methodology Results and discussion 2016/7/13 4 Methodology Results and discussion The vorticity distributions for these cases are presented in Fig. 8. 2016/7/13 5 Methodology Results and discussion For each of the case studied, four monitoring points were put in the computational domain at different locations to record the pressure parameter. These positions are shown in Fig. 9 and their coordinates are listed in Table 3. 2016/7/13 6 Methodology Results and discussion Fig. 10 compares the sound pressure levels at those four record points 00shown in Fig. 9 it is found that the installation of a spoiler structure may increase or 00reduce the sound pressure level. With an inappropriate spoiler design 00(cases 5 and 6), the sound pressure level may increase as much as 0020%. An appropriate design can subdue the production of sound 00pressure level by roughly 10% and also lower the lift coefficient. 2016/7/13 7 4. Summary 1. 2. 3. 4. Computational fluid dynamics (CFD) simulations of the transient flow field around a 2D cylinder and six vehicle models with different spoiler designs were presented and compared to relevant experimental data reported in the literature . Based on the cases considered in this work, the installation of a spoiler reduces the lift coefficient that leads to better conditions for high speed driving and improves the vertical stability of driving. The lift coefficient of case 4, which is approximately -0.001, is the lowest among all the cases studied. This indicates that the spoiler design of of disordered flow. case 4 has the best vertical stability. The spoiler configuration in case 4 represents the best design as far as the aerodynamics and aero-acoustics are concerned. 2016/7/13 8