Identification of Transition to Turbulence in a Highly Accelerated Start-Up Pipe Flow

[+] Author and Article Information
T. Koppel

Department of Mechanics, Tallinn University of Technology, Tallinn 19086, Estonia

L. Ainola

Department of Mathematics, Tallinn University of Technology, Tallinn 19086, Estonia

J. Fluids Eng 128(4), 680-686 (Dec 27, 2005) (7 pages) doi:10.1115/1.2201640 History: Received December 10, 2004; Revised December 27, 2005

The transition from a laminar to a turbulent flow in highly accelerated start-up pipe flows is described. In these flows, turbulence springs up simultaneously over the entire length of the pipe near the wall. The unsteady boundary layer in the pipe was analyzed theoretically with the Laplace transformation method and the asymptotic method for small values of time. From the experimental results available, relationships between the flow parameters and the transition time were derived. These relationships are characterized by the analytical forms. A physical explanation for the regularities in the turbulence spring-up time is proposed.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Development of the thickness of the boundary layer in start-up flows at the constant pressure gradients

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Figure 2

Layout of the experimental hydraulic system: 1–pump, 2–upper pressure tank (0.85m3), 3–cross sections for pressure measurements, 4–lower open tank (0.70m3), 5–quick-opening valve, 6–electromagnetic flowmeter, 7–cross section for wall shear stress measurements, and 8–cooling system

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Figure 3

Variation of the dimensionless transition time versus the dimensionless pressure gradient in a start-up flow at high acceleration

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Figure 4

Regions of laminar and turbulent flows in a highly accelerated start-up flow in the plane of the dimensionless mean velocity and the pressure gradient

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Figure 5

Regions of laminar and turbulent flows in a highly accelerated start-up flow in the plane of the dimensionless friction velocity and the pressure gradient




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