Abstract
The shear layer evolution and turbulent structure of near-wake behind a sphere atRe= 11,000 and 5,300 were investigated using a smoke-wire visualization method. A laminar flow separation was found to occur near the equator. The smooth laminar shear layers appeared to be axisymmetrically stable to the downstream location of aboutx/d=1.0 atRe=11,000 andx/d= 1.7∼1.8 atRe=5,300, respectively. At Re=11,000, the vortex ring-shaped protrusions were observed with the onset of shear layer instability. Moreover, the transition from laminar to turbulence in the separated flow region occurred earlier at the hiher Reynolds number ofRe=11,000 than atRe=5,300. The PIV measurements in the streamwise and cross-sectional planes atRe=11,000 clearly revealed the turbulent structures of the sphere wake such as recirculating flow, shear layer instability, vortex roll-up, and small-scale turbulent eddies.
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Sang Joon Lee: He received his Master’s and Ph.D. degrees in Mechanical Engineering from KAIST in 1982 and 1986, respectively. In 1986, he worked as a senior researcher at KIMM. He is currently a professor in the Department of Mechanical Engineering at POSTECH, which he has been with since 1987. His research interests are quantitative flow visualization (PIV, PTV, LIF, Holography, X-ray imaging), experimental fluid mechanics, bluff body aerodynamics, microfluidics, and bio-fluid flows.
Young Il Jang: He graduated from ROK Air Force Academy in 1995 and received his M.Sc. degree in Aerospace Engineering in 1998 from the Georgia Institute of Technology. After obtaining his M.Sc. Degree, he worked as an instructor at ROK Air Force Academy and is now working on his Ph.D degree at POSTECH, majoring in experimental fluid mechanics. His current research interest is the investigation of turbulent flow around a sphere.
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Jang, Y.I., Lee, S.J. Visualization of turbulent flow around a sphere at subcritical reynolds numbers. J Vis 10, 359–366 (2007). https://doi.org/10.1007/BF03181894
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DOI: https://doi.org/10.1007/BF03181894