Vortex Shedding

A phenomenon which can occur when a fluid flows past a flexible structure. In this situation, vortices are shed alternately to either side of the structure (assuming its long axis is perpendicular to the direction of flow) and an oscillating force results.

If the frequency of this force is close to a natural frequency of the structure, large displacements can result. The helical strakes often seen on large chimneys are installed to prevent wind-induced vortex shedding.

The effect is to produce turbulence with different length scales and hence a less constructive sound field or forcing of the structure.

See also: Aerodynamic Noise, Reynolds Number, Strouhal Number, Vortex.

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