Polymer turbulent drag reduction near the theta pointS. T. Lim1, C. H. Hong1, H. J. Choi1, Pik-Yin Lai2 and C. K. Chan2, 3
1 Department of Polymer Science and Engineering, Inha University - Incheon, 402-751, Korea
2 Department of Physics and Center for Complex Systems, National Central University Chungli, Taiwan 320, ROC
3 Institute of Physics, Academia Sinica - Nankang, Taipei, Taiwan 115, ROC
received 30 May 2007; accepted in final form 10 October 2007; published December 2007
published online 31 October 2007
Turbulent drag reduction efficiencies (%DR) of aqueous poly (ethylene oxide) solutions at various distances away from the theta temperature () are studied. It is found that only the long-time behavior of %DR of the system is sensitive to in that %DR decays faster for systems closer to the theta-point. Usually, this faster decay is attributed to the faster mechanical molecular degradation (MMD) of polymers in bad solvents produced by turbulence. However, temperature quenches experiments close to show that the apparent faster decrease in %DR for polymers closer to is not due to MMD but rather because of the shrinking of the polymer after they have been injected into the turbulent flow. The relative insensitivity of the initial maximum %DR can be understood if is considered as a function of the flow.
83.10.Tv - Structural and phase changes.
83.60.Yz - Drag reduction.
83.80.Rs - Polymer solutions.
© Europhysics Letters Association 2007