An experimental study of transitional pulsatile pipe flow
2012 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 24, no 1, 014103- p.Article in journal (Refereed) Published
The transitional regime of a sinusoidal pulsatile flow in a straight, rigid pipe is investigated using particle image velocimetry. The main aim is to investigate how the critical Reynolds number is affected by different pulsatile conditions, expressed as the Womersley number and the oscillatory Reynolds number. The transition occurs in the region of Re = 2250-3000 and is characterized by an increasing number of isolated turbulence structures. Based on velocity fields and flow visualizations, these structures can be identified as puffs, similar to those observed in steady flow transition. Measurements at different Womersley numbers yield similar transition behavior, indicating that pulsatile effects do not play a role in the regime that is investigated. Variations of the oscillatory Reynolds number also appear to have little effect, so that the transition here seems to be determined only by the mean Reynolds number. For larger mean Reynolds numbers, a second regime is observed: here, the flow remains turbulent throughout the cycle. The turbulence intensity varies during the cycle, but has a phase shift with respect to the mean flow component. This is caused by a growth of kinetic energy during the decelerating part and a decay during the accelerating part of the cycle. Flow visualization experiments reveal that the flow develops localized turbulence at several random axial positions. The structures quickly grow to fill the entire pipe in the decelerating phase and (partially) decay during the accelerating phase.
Place, publisher, year, edition, pages
2012. Vol. 24, no 1, 014103- p.
LAMINAR-TURBULENT TRANSITION, ASCENDING AORTA, BLOOD-FLOW, STABILITY, ONSET
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-91626DOI: 10.1063/1.3673611ISI: 000300527000023ScopusID: 2-s2.0-84856476930OAI: oai:DiVA.org:kth-91626DiVA: diva2:511857
QC 201203232012-03-232012-03-192012-03-23Bibliographically approved