Flow of Non-Newtonian Liquids under a Varying Pressure Gradient

Abstract

IN papers presented at the 1968 autumn meeting of the British Society of Rheology and the Fifth International Congress on Rheology held at Kyoto, Japan, in 1968, we discussed the flow behaviour of non-Newtonian liquids in straight pipes of circular cross-section under the action of a pressure gradient P which varied sinusoidally about a non-zero mean. We considered a pressure gradient of the form where R denotes the “real part”. We were particularly interested in the relation between the mean pressure gradient and the mean flow-rate. In particular we showed theoretically that, for a fixed frequency n, one should expect an increase in mean flow-rate (for a given mean pressure p̄) for low mean pressures and a decrease in mean flow-rate at higher values of p̄. The theoretical predictions also indicated a “resonance” effect where quite large percentage increases in mean flow-rate could be expected in the low mean-pressure region.