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Title: Instability of pulsatile flow for an axisymmetric stenotic tube.

Description: Pulsatile flow in axisymmetric vessels have a variety of different instability modes leading to localized turbulence at average flow speeds and pulse periods relevant to human physiology [1,2]. In addition, the flows can exhibit large transient growth of convective-type instabilities. Linearly unstable modes were first computed using Floquet analysis, followed up by direct numerical simulation as seen here. This particular type of instability is associated with alternating tilting of the vortex rings blown from the throat of the stenosis during successive pulses. Blue isosurfaces are of the discrimininat of the velocity gradient tensor, red and yellow isosurfaces are of positive/negative axial vorticity.

Credits: Hugh M Blackburn and Spencer J Sherwin

References: [1] Sherwin S.J. & Blackburn H.M. (2005) "Three-dimensional instabilities and transition of steady and pulsatile axisymmetric stenotic flows", J Fluid Mech 533: 297-327.

[2] Blackburn H.M. & Sherwin S.J. (2007) "Instability modes and transition of pulsatile stenotic flow: pulse-period dependence", J Fluid Mech 573: 57-88.

[3] Blackburn H.M., Sherwin S.J. & Barkley D. (2008) "Convective instability and transient growth in steady and pulsatile stenotic flows", J Fluid Mech 607: 267-277.

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Contributed By: Hugh Blackburn, Department of Mechanical & Aerospace Engineering, Monash University

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