Time-resolved analyses of the wake characteristics of two-dimensional bluff body flows have been executed by applying the multivision PIV to square prism (angle of attacks:0。, 30。), circular cylinders (rotating speed :0 rpm, 76 rpm) and airfoils (fixed, pitching) submerged in a circulating water channel (Re=10⁴). The macroscopic shedding patterns and their dominant frequencies were discussed in terms of instantaneous velocity, vorticity and turbulent quantities such as turbulence intensity, turbulent kinetic energy and three Reynolds stresses.
In this study, more realistic animation of flow patterns has been exploited by adopting the multivision PIV with three input CCD cameras to obtain an expanded measurement wake region. Quantitative frequency analysis was also carried out with the conventional PIV with single CCD camera.
Particularly, the time-averaged distribution of turbulent intensity in all experimental cases revealed separate island-like small regions where the magnitude of turbulent intensity was always strengthened. The dominant shedding frequencies of the turbulent quantities in the wake regions were two times larger than those of the velocity and vorticity.Abstract = ⅰ
Nomenclature = ⅲ
제1장 서론 = 1
1.1 연구의 배경 및 연구목적 = 1
1.2 PIV의 개요 = 3
1.3 Multivision PIV의 개요 = 6
제2장 실험 = 8
2.1 실험장치 = 8
2.2 균일유입 속도확인 = 14
2.3 PIV 시스템의 구성 = 16
2.3.1 조명 및 추적입자 = 16
2.3.2 영상입력 및 저장장치 = 17
2.3.3 이미지보오드 = 19
2.3.4 원통형 렌즈 = 20
제3장 영상처리 = 22
3.1 전처리 = 22
3.2 동일입자 추적 = 28
3.3 후처리 = 36
제4장 결과 및 검토 = 37
4.1 영상의 합성 = 37
4.2 속도벡터, 유선 및 속도프로파일 = 40
4.3 난류강도 = 50
4.4 제반 유동특성 = 55
4.5 시간평균 데이터 분석 = 58
4.6 주파수 분석 = 63
제5장 결론 = 72
참고문헌 = 74
감사의 글 = 7
