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point of inflexion

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Old   August 5, 2002, 00:20
Default point of inflexion
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Hi, Velocity profile of jet flow has a point of inflexion, what its mean and why jet flow has a point of inflexion. Thanks
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Old   August 6, 2002, 04:09
Default Re: point of inflexion
Lionel Larcheveque
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Because of the existence of an inflection point for the mean velocity profile, jet flows as shear layers and wakes are subject to Kelvin-Helmholtz instabilities (Rayleigh's inflection point criterion). It results in periodic vortices shedding (sometime called coherent structures) growing and pairing while convected in the streamwise direction. If the convection velocity is supersonic with regards to the external flow, these structures can generates Mach waves (somehow similar to shock waves) and emit very strong noise.

For further informations, see for instance: P. Huerre and M. Rossi, Hydrodynamic instabilities in open flows, in "Hydrodynamics and nonlinear instabilities", edited by C. Godreche and P. Manneville, pp 81-214, Cambridge University Press, 1998.

Hope this helps.
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