Showing papers by "Kenneth Walters published in 1969"
TL;DR: In this article, the authors considered a pressure gradient of the form where R denotes the real part and showed theoretically that, for a fixed frequency n, one should expect an increase in mean flow-rate (for a given mean pressure p) for low mean pressures and a decrease in flow rate at higher values of p.
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 p) for low mean pressures and a decrease in mean flow-rate at higher values of p. 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.
57 citations
TL;DR: In this paper, an experimental study is described which seeks to assess the effect of elasticity on the flow of elastico-viscous liquids as they are made to flow through curved pipes under a pressure gradient.
Abstract: An experimental study is described which seeks to assess the effect of elasticity on the flow of elastico-viscous liquids as they are made to flow through curved pipes under a pressure gradient. Wherever possible, the experimental results are discussed in the light of existing theoretical predictions and good agreement between theory and experiment for viscous and elastico-viscous liquids is indicated. The general flow pattern for elastico-viscous liquids is shown to be similar to that for Newtonian liquids consisting of two spirals separated by the central plane. Elasticity has a significant effect on the pitch of these spirals. The flow rate in the case of laminar flow and in the transition region between laminar and turbulent flow is significantly enhanced by the presence of elasticity in the liquids, but the opposite is the case in turbulent flow at high Reynolds numbers. Many materials of industrial importance can be classified as elastico-viscous liquids in the sense that they flow under the action of applied stresses and yet have some of the properties usually associated with solids. In technological processes, these elastico-viscous liquids are often pumped through pipes which are usually straight but are sometimes curved. It is therefore of some practical importance to study the behaviour of elastico-viscous liquids as they are made to flow through straight and curved pipes under the action of a pressure gradient. The flow of viscous and elastico-viscous liquids through straight pipes is well documented, but very little consideration appears to have been given to the flow of elastico-viscous liquids through curved pipes. In the present paper, we shall indicate the various interesting features which have arisen from an experimental study of the flow of elastico-viscous liquids through straight and curved pipes of circular cross-section. Our work has been primarily motivated by technological requirements, but it may have applications in other spheres. For example, it may throw light on the flow of blood in the larger capillaries, since it is known that whole blood is non-Newtonian in its behaviour.
41 citations