Drag Reduction by Polymers in Saline Nutrient Solutions

Abstract

Drag reduction (DR) by polymers has several industrial applications, and it has also shown to produce beneficial effects on blood circulation and may represent a way to treat cardiovascular disorders. Concerning medical applications, there are basically two types of studies using drag reducing polymers (DRP), i.e., in vitro and in vivo. Although blood may be used in the in vitro studies, there are several limitations, such as incompatibility of Rh and possibility of denaturing blood proteins. Thus, biomedical researchers commonly use an artificial plasma-like saline nutrient solution (SNS), which contains ions, nutrients, a buffer to maintain pH levels and a supply of oxygen to the tissue. The behavior of the DRP in water is well reported in the literature, but the SNS components can interact with the polymers, changing their capacity to reduce drag. This study investigates the behavior of three different polymers, i.e., polyacrylamide (PAM), polyethylene oxide (PEO), and xanthan gum (XG), when applied as DRP to a commonly used SNS. For the conditions evaluated, the SNS composition does not change significantly PAM and PEO behavior, showing that they can be satisfactorily diluted in this solvent without loss of efficiency as drag reducers. However, it modifies XG conformation, drastically reducing its efficiency. The experiments with tail arterial beds suggest that PAM is efficient to reduce the perfusion pressure, but PEO and XG do not seem to be good reducers under the experimental conditions that have been analyzed, possibly due to the interaction of the drag reducers with the flow, with the solvent components and with the tissues that were kept alive during the experiments. Although PEO did not present a good performance as DRP for the conditions evaluated in the perfusion tests, its performance can be improved in other organs where the turbulence levels, or instabilities, are higher, as suggested by the rheometer tests.