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Instabilities in Pulsating Pipe Flow of Shear-Thinning and Shear-Thickening Fluids
Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
2012 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this study, we have considered the modal and non-modal stability of fluids with shear-dependent viscosity flowing in a rigid straight pipe. A second order finite-difference code is used for the simulation of pipe flow in the cylindrical coordinate system. The Carreau-Yasuda model where the rheological parameters vary in the range of 0.3 < n < 1.5 and 0.1 < λ < 100 is represents the viscosity of shear- thinning and shear thickening fluids. Variation of the periodic pulsatile forcing is obtained via the ratio Kω/Kο and set between 0.2 and 20. Zero and non-zero streamwise wavenumber have been considered separately in this study.

For the axially invariant mode, energy growth maxima occur for unity azimuthal wave number, whereas for the axially non-invariant mode, maximum energy growth can be observed for azimuthal wave number of two for both Newtonian and non-Newtonian fluids. Modal and non-modal analysis for both Newtonian and non-Newtonian fluids show that the flow is asymptotically stable for any configuration and the pulsatile flow is slightly more stable than steady flow. Increasing the maximum velocity for shear-thinning fluids caused by reducing power-low index n is more evident than shear-thickening fluids. Moreover, rheological parameters of Carreau-Yasuda model have ignored the effect on the peak velocity of the oscillatory components. Increasing Reynolds number will enhance the maximum energy growth while a revers behavior is observed by increasing Womersley number.

Place, publisher, year, edition, pages
2012. , 40 p.
Keyword [en]
Stability, Pulsatile pipe, Transient Growth, Floquet Multiplier, Modal and non-Modal Stability
National Category
Mechanical Engineering
URN: urn:nbn:se:liu:diva-82037ISRN: LIU-IEI-TEK-A--12/01360--SEOAI: diva2:557622
Subject / course
Mechanical Engineering
Available from: 2012-10-03 Created: 2012-09-28 Last updated: 2012-10-03Bibliographically approved

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Sadrizadeh, Sasan
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