표제지
목차
Nomenclatures 9
I. 서론 10
1.1. 연구배경 10
1.2. 관련 연구 15
1.3. 연구목적 17
1.4. 연구방법 17
II. 해석이론 18
2.1. 지배방정식 18
2.2. 자동차에 작용하는 힘 19
III. 유동해석 방법 및 모델 21
3.1. 유동해석 방법 21
3.1.1. 격자생성(Mesh Generation) 21
3.1.2. 경계조건(Boundary Conditions) 22
3.2. 유동해석 모델별 해석변수 23
3.2.1. 리어 디퓨저의 각도변화 모델 23
3.2.2. 리어 디퓨저 디바이더 개수 변화 모델 24
IV. 유동해석 결과 25
4.1. 리어 디퓨저 각도변화에 대한 유동해석 결과 25
4.1.1. 항력계수 특성 26
4.1.2. 양력계수 특성 29
4.1.3. 최적 리어 디퓨저 각도에서의 항력 및 양력계수 비교 32
4.1.4. 해석결과 요약 32
4.2. 리어 디퓨저 디바이더 개수 변화에 대한 유동해석 결과 41
4.2.1. 항력계수 특성 42
4.2.2. 양력계수 특성 45
4.2.3. 최적 리어 디퓨저 디바이더에서의 유동특성 비교 48
4.2.4. 해석결과 요약 49
V. 결론 67
참고문헌 69
국문요약 71
ABSTRACT 72
Table 1-1. Analysis variables list for the flow analysis 17
Table 3-1. Mesh statistics of rear diffuser without divider 22
Table 4-1. CD & CL variation according to the change of diffuser angle at 80km/h[이미지참조] 25
Table 4-2. CD & CL variation according to the change of diffuser angle at 100km/h[이미지참조] 25
Table 4-3. CD & CL variation according to the change of diffuser angle at 120km/h[이미지참조] 25
Table 4-4. CD & CL variation according to the change of diffuser angle at 140km/h[이미지참조] 25
Table 4-5. CD & CL variation according to the change of divider no. at 80km/h[이미지참조] 41
Table 4-6. CD & CL variation according to the change of divider no. at 100km/h[이미지참조] 41
Table 4-7. CD & CL variation according to the change of divider no. at 120km/h[이미지참조] 41
Table 4-8. CD & CL variation according to the change of divider no. at 140km/h[이미지참조] 41
Fig. 1-1. Application of car rear diffuser 11
Fig. 1-2. Down-force on the car by the difference of pressures 12
Fig. 1-3. Pressure coefficient distribution in the bottom of a car 13
Fig. 1-4. Relation of pressure and velocity in the bottom of car 13
Fig. 1-5. Low pressure formation region of rear diffuser 14
Fig. 2-1. Friction and pressure drag 20
Fig. 2-2. Drag and lift force on the car 20
Fig. 3-1. Computational domain of CFD analysis of rear diffuser 21
Fig. 3-2. Mesh generation of CFD analysis of rear diffuser 22
Fig. 3-3. Boundary conditions for CFD analysis of rear diffuser 22
Fig. 3-4. Analysis model of rear diffuser angle effect 23
Fig. 3-5. Modeling for the effect of rear diffuser angle 23
Fig. 3-6. Five models of rear diffuser with divider 24
Fig. 4-1. Graph of CD versus diffuser angle at U=80km/h[이미지참조] 26
Fig. 4-2. Graph of CD versus diffuser angle at U=100km/h[이미지참조] 27
Fig. 4-3. Graph of CD versus diffuser angle at U=120km/h[이미지참조] 27
Fig. 4-4. Graph of CD versus diffuser angle at U=140km/h[이미지참조] 28
Fig. 4-5. Graph of CD versus diffuser angle according to the velocity variation[이미지참조] 28
Fig. 4-6. Graph of CL versus diffuser angle at U=80km/h[이미지참조] 29
Fig. 4-7. Graph of CL versus diffuser angle at U=100km/h[이미지참조] 30
Fig. 4-8. Graph of CL versus diffuser angle at U=120km/h[이미지참조] 30
Fig. 4-9. Graph of CL versus diffuser angle at U=140km/h[이미지참조] 31
Fig. 4-10. Graph of CL versus diffuser angle according to the velocity variation[이미지참조] 31
Fig. 4-11. Variation graph of CD and CL versus car velocity at diffuser angle 6°[이미지참조] 32
Fig. 4-12. Distribution of velocity streamlines at U=80km/h according to the change of...[이미지참조] 34
Fig. 4-13. Distribution of velocity streamlines at U=100km/h according to the change of...[이미지참조] 36
Fig. 4-14. Distribution of velocity streamlines at U=120km/h according to the change of...[이미지참조] 38
Fig. 4-15. Distribution of velocity streamlines at U=140km/h according to the change of...[이미지참조] 40
Fig. 4-16. Graph of CD versus no. of divider at U=80km/h[이미지참조] 42
Fig. 4-17. Graph of CD versus no. of divider at U=100km/h[이미지참조] 43
Fig. 4-18. Graph of CD versus no. of divider at U=120km/h[이미지참조] 43
Fig. 4-19. Graph of CD versus no. of divider at U=140km/h[이미지참조] 44
Fig. 4-20. Graph of CD versus no. of divider according to the velocity variation[이미지참조] 44
Fig. 4-21. Graph of CL versus no. of divider at U=80km/h[이미지참조] 46
Fig. 4-22. Graph of CL versus no. of divider at U=100km/h[이미지참조] 46
Fig. 4-23. Graph of CL versus no. of divider at U=120km/h[이미지참조] 47
Fig. 4-24. Graph of CL versus no. of divider at U=140km/h[이미지참조] 47
Fig. 4-25. Graph of CL versus no. of divider according to the velocity variation[이미지참조] 48
Fig. 4-26. Comparison of CL with 3 dividers and without divider[이미지참조] 49
Fig. 4-27. Comparison of velocity vector distribution at the rear of car in case of U=120km/h 50
Fig. 4-28. Comparison of velocity streamlines distribution at the rear of car in case of U=120km/h 50
Fig. 4-29. Comparison of turbulence kinetic energy distribution at U=120km/h 52
Fig. 4-30. Comparison of turbulence kinetic energy distribution at U=140km/h 54
Fig. 4-31. Comparison of vortex-core region in the swirling strength 0.01 at U=120km/h 55
Fig. 4-32. Comparison of vortex-core region in the swirling strength 0.01 at U=140km/h 55
Fig. 4-33. Comparison of vortex-core region in the swirling strength 0.005 at U=120km/h 56
Fig. 4-34. Comparison of vortex-core region in the swirling strength 0.005 at U=140km/h 56
Fig. 4-35. Distribution of velocity streamlines at U=80km/h to the change of... 59
Fig. 4-36. Distribution of velocity streamlines at U=100km/h to the change of divider number 61
Fig. 4-37. Distribution of velocity streamlines at U=120km/h to the change of divider number 64
Fig. 4-38. Distribution of velocity streamlines at U=140km/h to the change of divider number 66