Friction loss in unsteady laminar and turbulent flows in smooth round pipes

Shuy, Eng Ban (1986). Friction loss in unsteady laminar and turbulent flows in smooth round pipes PhD Thesis, School of Engineering, The University of Queensland. doi:10.14264/uql.2015.34

       
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Author Shuy, Eng Ban
Thesis Title Friction loss in unsteady laminar and turbulent flows in smooth round pipes
School, Centre or Institute School of Engineering
Institution The University of Queensland
DOI 10.14264/uql.2015.34
Publication date 1986-01-01
Thesis type PhD Thesis
Supervisor C. J. Apelt
Total pages 408
Language eng
Subjects 020303 Fluid Physics
Formatted abstract
The main objective of the research program is to derive, through theoretical and experimental studies, accurate and practical equations for the wall shear stress in unsteady laminar and turbulent flows in smooth round pipes.

The governing differential equations for different types of unsteady pipe flows are derived systematically from the fundamental equations of fluid dynamics. The governing equations for laminar flows are solved mathematically to yield an explicit, one-dimensional equation for the unsteady wall shear stress, which can be applied to general non-periodic and low frequency periodic oscillating and pulsating flows. The accuracy and validity of the equation are verified by comparing its predictions with exact analytical solutions for a few types of unsteady laminar flows. A simple approximate equation for the wall shear stress in oscillating and pulsating flows is also derived which is accurate to within 0.5% of the exact solution over the whole range of frequency.

The governing equations for turbulent flows are solved numerically by using an implicit finite difference scheme. A geometrically graded radial grid and a viscosity distribution which is computed 'dynamically' at each time step, are used in the solution. The solution procedure adopted allows simple and accurate computation of the wall shear stress, and gives consistently convergent solutions even at relatively coarse grid spacings.

An experimental rig was designed to allow, for the first time, direct mechanical measurement of the wall shear stress in unsteady turbulent flows. The transient mean velocity and pressure gradient were also measured- to allow the wall shear stress to be computed indirectly for comparison. From the test results, an empirical equation for the unsteady wall shear is proposed.

The unsteady wall shear equations are applied to the analysis of water hammer transients in pipe systems and free-oscillating flows in U-shaped tubes. The effect of friction modelling on the solutions is examined, and suitable unsteady friction equations for practical applications are recommended.
Additional Notes Other Title: Friction loss in unsteady flow in pipes.

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
 
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