Effect of Entrance Region on Laminar Startup Flow in Pipes

[+] Author and Article Information
H. I. Andersson, R. Kristoffersen

Division of Applied Mechanics, Norwegian Institute of Technology, N-7034 Trondheim-NTH, Norway

J. Appl. Mech 55(2), 482-486 (Jun 01, 1988) (5 pages) doi:10.1115/1.3173703 History: Received March 09, 1987; Revised February 01, 1988; Online July 21, 2009


The ultimate effects of the entrance region on startup flow are considered by one-dimensional steady-state analysis. By roughly accounting for the entrance loss, semiempirical formulas for the average velocity and the hydrodynamic entrance length in terms of a startup flow parameter and an entrance effect coefficient are provided. The startup flow parameter M = gHD4 /2048v2 L2 is identified as the fundamental parameter of the problem. While Szymanski’s solution is recovered in the long pipe limit, i.e., M → 0, the steady-state volume flux through short pipes (M > 0.05) is significantly reduced due to entrance region effects.

Copyright © 1988 by ASME
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