Effects of hydrophobic modification of xanthan gum on its turbulent drag reduction characteristics

Abstract

Abstract The effects of different structures of biopolymeric xanthan gum (XG) on its drag reduction (DR) in turbulent flow in an aqueous solution with pristine XG and XG modified by grafting octylamine were examined. Owing to the more rigid conformation of hydrophobically modified XG, its chemical modification allowed a study of the impact of chain flexibility on DR and mechanical degradation. The measurements were carried out at four XG concentrations using a high-precision rotating disk apparatus as a function of time at 1980 rpm. The results showed that the flexibility and concentration with a similar molecular weight affect the DR. Time-dependent DR efficiency was fitted and rheological characteristics of the XG (0.01 wt%) were examined using a rotational rheometer. The influence of the flexibility of the XGs on turbulent DR were compared and analyzed according to these observations.