Empirical Model-based MOE for Friction Reduction by Slot-Ejected Polymer Solutions in an Aqueous Environment.

摘要

Since the discovery of the Toms Effect in 1948, many investigators have explored the nature and causes of polymer-induced friction reduction, using both experimental and theoretical methods. External friction reduction for use on submarines and other marine vehicles is an area of great practical importance. In such applications, the polymer must be ejected at one or more locations along the vehicle's exterior surface, so the effects of non-uniform polymer concentration are paramount. The goal of this work was to develop a model that accurately captures the drag-reduction behavior of slot-ejected polymer in external flow and that can be used as a measure of effectiveness (MOE) for engineering purposes. An empirical model has been developed by combining partial models from the work of earlier researchers. These model components were combined, using simple subsidiary calculations, to create a complete model of friction reduction as a function of the dimensionless parameter K. The complete model contains several empirical parameters from earlier published works and several operating parameters that define an experimental configuration. Each of the parameters was tested for its impact on the model. It was found that the model was very sensitive to three parameters in particular: the power law exponent that governs the approach to saturation as a function of polymer concentration, the ejection angle of the slot that extrudes the polymer into the flow, and the roll-off concentration at which performance decreases for high polymer concentrations. The model provides a useful MOE tool for evaluation of field experiments and for design of slot ejector systems.