Extensional Viscosity of a Semi-dilute Polymer Solution Effect on Two-dimensional Turbulence
Ruri Hidema, Hiroshi Suzuki, Yoshiyuki Komoda and Hidemitsu Furukawa
An experimental study has been performed in order to investigate the relationship between the extensional viscosity of polymers and the turbulent drag reduction. Polyethyleneoxide, as a flexible polymer, and hydroxypropyl cellulose, as a rigid rod-like polymer, were added to the two-dimensional turbulence that was visualized by the interference pattern of flowing soap films and were analyzed using a novel single-image analysis. The distributions of the velocity fluctuations in the turbulence were calculated by the curvatures of the interference patterns. The distribution became narrower by the addition of polymers. The power spectra of interference images were also obtained, which is related to fluctuations of the water layer in turbulence. The power spectra exhibit a scaling behavior, and the power components give information on the energy transfer in turbulence. The results indicated that the mechanisms of energy transfer are different in the streamwise and normal directions, which is related to the flexibility and extensional viscosity of the polymers.
Keywords: Extensional viscosity, Drag reduction, Polymer solution, Two-dimensional turbulence, Flow visualization, Image processing.