Laminar and turbulent flow in annuli of unit eccentricity

Abstract

AbstractExperimental results are presented for the flow of water in eccentric annuli having unit eccentricity in the laminar, transition and turbulent flow regimes at Reynolds numbers between 200 and 20,000. In both the laminar and turbulent regimes the interesting result is obtained that, for a given Reynolds number, the friction factor is a minimum at a diameter ratio of about 0.750. The experimental results are compared with previous theoretical analyses in the laminar region, and with previous experimental data at Reynolds numbers exceeding 20,000 in the turbulent region. A further interesting result relates to the transition region where, at intermediate diameter ratios, the transition from laminar to turbulent flow becomes more diffuse. This appears to be a consequence of the gradual change from laminar to turbulent flow brought about by the variation in local Reynolds number from zero to a maximum value within the eccentric annulus. It is believed that sufficent experimental data are now available for the pressure gradient to be predicted for flow in eccentric annuli of unit eccentricity over a relatively wide range of Reynolds number.