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Near wake structure behind a 3D square prism with the aspect ratio of 2.7 in a shallow boundary layer flow
Abstract Three dimensional structures of unsteady flows behind a square prism with aspect ratio H/D=2.7 in a shallow boundary layer flow are investigated by two dimensional and three dimensional stereoscopic PIV techniques synchronizing with velocity measurement by a hot wire anemometer. According to the conditional PIV image sampling technique conducted by using the velocity signal measured outside the separated shear layer, it becomes clear that an arch-type vortex is formed behind the prism throughout a cycle of the Kármán vortex formation and shedding. As the vortex grows and moves downstream, the vortex line stretches in a stream-wise direction near the tip of the vortex which does not move and stays still just behind the prism throughout a cycle. According to POD analysis, the wake fluctuates very slowly with a period of approximately 6 times of that of the Kármán vortex shedding.
Highlights ► Velocity vectors in wake behind a square prism were measured by 2D and 3D stereoscopic PIV. ► Velocity vectors in the wake were conditionally sampled synchronizing with Karman vortex shedding. ► An arch type vortex was observed throughout a cycle of Karman vortex formation.
Near wake structure behind a 3D square prism with the aspect ratio of 2.7 in a shallow boundary layer flow
Abstract Three dimensional structures of unsteady flows behind a square prism with aspect ratio H/D=2.7 in a shallow boundary layer flow are investigated by two dimensional and three dimensional stereoscopic PIV techniques synchronizing with velocity measurement by a hot wire anemometer. According to the conditional PIV image sampling technique conducted by using the velocity signal measured outside the separated shear layer, it becomes clear that an arch-type vortex is formed behind the prism throughout a cycle of the Kármán vortex formation and shedding. As the vortex grows and moves downstream, the vortex line stretches in a stream-wise direction near the tip of the vortex which does not move and stays still just behind the prism throughout a cycle. According to POD analysis, the wake fluctuates very slowly with a period of approximately 6 times of that of the Kármán vortex shedding.
Highlights ► Velocity vectors in wake behind a square prism were measured by 2D and 3D stereoscopic PIV. ► Velocity vectors in the wake were conditionally sampled synchronizing with Karman vortex shedding. ► An arch type vortex was observed throughout a cycle of Karman vortex formation.
Near wake structure behind a 3D square prism with the aspect ratio of 2.7 in a shallow boundary layer flow
Kawai, Hiromasa (author) / Okuda, Yasuo (author) / Ohashi, Masamiki (author)
Journal of Wind Engineering and Industrial Aerodynamics ; 104-106 ; 196-202
2012-01-01
7 pages
Article (Journal)
Electronic Resource
English
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