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Approximate wall shear equation for unsteady laminar pipe flows

Author(s): E.B. Shuy

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Abstract: An approximate equation is derived for wall shear stress in unsteady laminar pipe flows in terms of the instantaneous section mean velocity and acceleration. The equation, which is exact for a constantly accelerating or decelerating flow, is applied to solve for two types of pressure gradient functions, a transient start-up flow and a linearly reversing pressure gradient. Comparison with exact analytical solutions verifies that the equation is adequate for the two types of transient flows investigated, and for low frequency oscillating flows.

DOI: https://doi.org/10.1080/00221689509498655

Year: 1995

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