The production of turbulence near a wall is the governing mechanism of the turbulent drag from external flow around bodies and in internal flows involving turbulence. The pocket is closely associated with the occurrence of the large Reynolds stress producing motions, and therefore implicitly involved with the turbulence production process. Within the wall region, hot-wire measurements show that a strong vortex forms within the pockets. This vortex is the rearrangement of existing sublayer vorticity and its amplification. The work in this area has been applied to the prediction and reduction of drag. The study is focused on the time scale of the pockets. The relationship between pocket time scale and modified wall has been found. By changing the upstream boundary condition at the wall the time scale of pockets were increased.
목차
ABSTRACT 기호설명 1. 서론 2. 실험장치 및 방법 2.1 속도 데이터 취득 시스템 2.2 고속 사진촬영 시스쳄 2.3 가시화 마커 분사 2.4 밝은 조명 2.5 저속 풍동 2.6 벽면의 형상 변화 2.7 평균속도 프로파일 데이타 처리 기술 2.8 가시화 데이터 3. 결과 및 고찰 3.1 평균속도 프로파일 데이터 3.2 포켓 time scale 4. 결론 References
키워드
수동적 표면 형상변화서브레이어열선 프로브난류 드래그 저감벽면 위 유동Passive surface modificationSublayerHot-wire probeTurbulence drag reductionWall bounded flow
저자
유성출 [ Seoung-Chool Yoo | Member, Professor, Dept., of mechanical & automotive Engr., Halla University ]
Corresponding Author