Anomalous Pitot tube and hot film measurements in dilute polymer solutions

Abstract

The experiments reported show that Pitot tubes and hot film cylinders behave anomalously in the turbulent flow of dilute polymer solutions. The discrepancy in the Pitot tube readings increases with the absolute velocity, the molecular weight and concentration of polymer, and with decreasing Pitot tube diameter. This discrepancy is also a function, as yet undetermined, of the ambient strain rate. Hot film measurements indicate that for cylinders in cross flow the heat transfer is poorer in polymer solutions than in the solvent and exhibits abrupt transitions over which the heat transfer coefficient may vary by threefold. The heat transfer improves with increasing ambient strain rate and with decreasing polymer molecular weight.