The effect of ultrahigh shear rate on the physical characteristics of xanthan gum.

Xanthan gum is an important high polymer for turbulent drag reduction in fluid engineering applications, but the drag reduction characteristics will disappear with ultrahigh rotating shear. To further reveal this phenomenon, the average shear rate is proposed with the energy dissipation theory to explore drag reduction and rheological characteristics of the polymers in an ultrahigh rotating shear experimental system. The results indicate that the shear leads to the mechanical degradation of the polymer, further increasing the ultrahigh shear rate. A higher shear rate accelerates the degradation of the polymer solution and makes it approach Newtonian fluid, decreasing drag reduction characteristics. Besides, it is found that the ideal addition concentration is 3500 ppm, at which the relative degradation degree is globally slightest, and the relative degradation rate is locally smallest. Understanding these characteristics could help select the ideal concentration of polymers and add polymers regularly to maintain the drag reduction efficiency during ultrahigh rotating shear. [ABSTRACT FROM AUTHOR]