Vortex shedding - Flow visualisation

The flow past a bluff body can be a complicated fluid flow situation. At relatively large Reynolds numbers, an alternating vortex shedding takes place in the wake. Around the bluff body, the separation points shift forward and backward alternately. These oscillations cause vortices to be shed alternately from one side to the other of the bluff body, resulting in a pattern of vortices rotating in opposite directions behind the body. The movement of the separation points causes an oscillating pressure at the cylinder surface which in turn may cause structural vibrations transverse to the free-stream.
The following experiments illustrate a range of flow visualisations of vortex shedding behind bluff body:
• bluff body in shallow free-surface flow
• self-sustained oscillation of a pendulum in direction normal to flow
• square cylinder in a wind tunnel
The vortex shedding behind a bluff body is a classical illustration of form drag and wake flow. It can generate some fascinating flow pattern, e.g. von Karman street of vortices.
A basic understanding of the fluid dynamics processes is critical in many real-word applications including engineering infrastructures. These discussed in a number of relevant UA-cam video movies in the same Playlist at:
{ / @hubert_chanson }
Fluid mechanics and hydraulics in Hubert Chanson UA-cam channel { / @hubert_chanson }
Applied hydrodynamics [Playlist]
Advanced hydraulics of open channel flows [Playlist]
Streamlines { • Streamlines }
Reynolds number { • Reynolds number }
Von Karman street of vortices (1) Presentation { • Von Karman Street of V... }
Von Karman street of vortices (2) Experimental observations { • Von Karman Street of V... }
Von Karman street of vortices (3) Mitigation measures { • Von Karman Street of V... }
Acknowledgements
Prof. Colin J. APELT
Jason VAN DER GEVEL
Stewart MATTHEWS
CIVL4160 students
References
VALLENTINE, H.R. (1969). "Applied Hydrodynamics." Butterworths, London, UK, SI edition.
SCHLICHTING, H. (1979). "Boundary Layer Theory." McGraw-Hill, New York, USA, 7th edition.
VAN DYKE, M. (1982). "An Album of Fluid Motion." Parabolic Press, Stanford CA, USA, 176 pages.
CHANSON, H. (2014). "Applied Hydrodynamics: An Introduction." CRC Press, Taylor & Francis Group, Leiden, The Netherlands, 448 pages & 21 video movies (ISBN 978-1-138-00093-3).