Title: Laminar-to-Turbulent Transition of Pipe Flows Triggered by Wall-Mounted, Ring-Type Obstacles
Authors: Durst, Franz
Breuer, Michael  
Ünsal, Bülent
Haddad, Kais
Language: eng
Keywords: Pipe flow;Laminar;Transition;Turbulent;Triggering by ring-type obstacle
Issue Date: 29-Jun-2022
Publisher: Taylor & Francis
Document Type: Article
Source: JOURNAL OF TURBULENCE 2022, VOL. 23, NO. 7, 382–404 https://doi.org/10.1080/14685248.2022.2092121
Journal / Series / Working Paper (HSU): Journal of Turbulence
Volume: 23
Issue: 7
Page Start: 382
Page End: 404
Abstract: 
The literature stresses the inherent stability of laminar pipe flows with
parabolic velocity profiles and this paper refers to the relevant publi-
cations summarizing this work. To cause such flows to turn into their
turbulent state requires laminar pipe flows to be triggered exter-
nally. Ring-type, wall-mounted obstacles can be used for this pur-
pose, and investigations in this area are of particular interest to the
authors’ work, summarized in this paper. In the investigations pre-
sented here, however, a special triggering technique was employed
that allowed laminar pipe flows to be exposed to obstacle distur-
bances for only about 30 ms. Individual puffs and slugs could be pro-
duced in this way. Comparisons with fixed wall-mounted obstacles
showed that the properties of both types of turbulent slugs were the
same. Theoretical derivations are described to provide the required
obstacle height as a function of the Reynolds number, to trigger
fully developed laminar pipe flows to turn into their turbulent state.
Corresponding experimental investigations were also performed as
described. Very good agreement between the theoretical and exper-
imental results was obtained. All this demonstrates that a relatively
simple ‘ad hoc theory’ can derive the required height of ring-type,
wall-inserted obstacles to trigger laminar pipe flows with parabolic
velocity profiles to turn turbulent. Other ways to trigger laminar pipe
flows to turn turbulent were also investigated by employing blow-
ers and plenum chambers and varying the lengths and diameters
of pipes. It is demonstrated, in a somewhat qualitative way, that the
maintenance of laminar pipe flows requires all components of a test
rig to be matched to each other to maintain pipe flows laminar.
Organization Units (connected with the publication): Strömungsmechanik 
Publisher DOI: 10.1080/14685248.2022.2092121
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