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The Scruton number Sc is an important parameter for vortex-induced vibration (excitation) of structures, vibrations caused by rain or wind, dry inclined cable galloping, and wake galloping, the unstable airflow that forms around bridge cables and other cylindrically-structured buildings.[1] It is named after Christopher "Kit" Scruton, a British industrial dynamics engineer.[2][3]

It is defined by:[4]


is the structural damping expressed by the logarithmic damping decrement,
is the effective mass per unit length,
is the density of the air, or liquid,
is the characteristic width of the structure.


  1. ^ "MECHANICS OF WIND-INDUCED VIBRATIONS". Federal Highway Administration Research and Technology. August 2007. Retrieved 17 January 2017.
  2. ^ Wenzel, Helmut (2008). Health Monitoring of Bridges. Wiley. p. 464. ISBN 978-0-470-74018-7.
  3. ^ Ted Stathopoulos; Charalambos C. Baniotopoulos (31 December 2007). Wind Effects on Buildings and Design of Wind-Sensitive Structures. Springer Science & Business Media. p. 45. ISBN 978-3-211-73076-8.
  4. ^ Hansen, Svend O. (2–7 November 2007). Vortex-induced vibrations of structures (PDF). Structural Engineers World Congress 2007. Bangalore, India. Retrieved 5 March 2021.