Modification of the Wake of a Cylinder: Effect of Small Amplitude Surface Perturbation (Technology #: 040506-01)

Lehigh University Office of Technology Transfer
posted on 07/10/2009

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Alternate shedding of vortices from long slender structures may cause vortex induced vibration leading to fatigue type failure of the body by imposing periodic pressure changes on its surface. The invention of attenuation of regular formation of vortex shedding is achieved.  The presence of a bi-stable instability has been discovered for cylinders with a surface modification. At this particular unstable configuration,

*Flow lies between two different stable states

*Regular Karman vortex shedding stops

*Shear layer flapping arises at a broadband low frequency.

This technology involves the use of a surface modification to a cylinder to attenuate vortex induced vibration caused by flows at a certain angle of attach and velocity. 

Advantages

In this system, according to the flow situation, the perturbation can be brought to the critical position that stops Karman vortex shedding.  Flows of varying angle of attach and velocity may use this technology by modifying the method via using an automated system. 

Applications

*Heat exchanger tubes

*Slender structures on petrol drilling platforms

*Bridge piers

*Chimney stacks

*Other slender structures