Flow Pattern and Frictional Losses in Pulsating Pipe Flow : Part 6 Frictional Losses In a Laminar Flow

Abstract

Relations between frictional losses and dimensionless frequency in an incompressible pulsating laminar pipe flow are investigated in terms of three kinds of friction factors. Furthermore, the frictional losses calculated from previously reported various approximate representations for wall shear stress are compared with those calculated from an analytical one in order to examine the validity of approximations. It becomes evident that the behaviours of instantaneous and time average friction factors in the quasi-steady, the intermediate, and the inertia dominant regions are qualitatively similar to those in a pulsating turbulent pipe flow and that the time average friction factor and the root mean square friction factor proposed here can be correlated to time-averaged cross-sectional mean viscous dissipation, while the instantaneous friction factor cannot represent the instantaneous cross-sectional mean viscous dissipation except for the quasi-steady region.