FLOW PATTERN AND FRICTIONAL LOSSES IN PULSATING PIPE FLOW - 2. EFFECT OF PULSATING FREQUENCY ON THE TURBULENT FRICTIONAL LOSSES.

Abstract

The effect of frequency on frictional losses in a pulsating turbulent pipe flow is investigated. The frictional losses estimated from flow pattern diagrams agree well with those obtained experimentally at the time-averaged Reynolds number of about 5. 7 multiplied by 10**4 and over wide ranges of both frequency and velocity amplitude ratio A//1. As is expected, the instantaneous friction factor lambda // mu (t) and the quasi-steady friction factor lambda //q are almost equal in the quasi-steady region indicated in a previous paper. With an increasing dimensionless frequency omega prime , however, the instantaneous friction factor is either larger or smaller than the quasi-steady friction factor in both accelerating and decelerating zones of a pulse cycle. The time average friction factor lambda // mu //,//t//a, which is a function of omega prime and A//1, is always larger than the friction factor lambda //s for a steady flow with equivalent mean Reynolds number and increases monotonically with omega prime and A//1.