Time dependence of turbulent drag reduction efficiency of polyisobutylene in kerosene

Turbulent flow of kerosene, which is driven by a rotating disk in a closed chamber, shows significant drag reduction when tiny amount of an oil-soluble polyisobutylene (PIB) was added. Effect of experimental parameters such as Reynolds number (Re) and temperature on the time dependence of drag reduction was investigated, in which turbulent drag reduction efficiency for the PIB–kerosene solution was found to decrease with time due to mechanical degradation of the polymer chains induced by severe turbulent flow. The change in drag reduction efficiency was fitted well with two model equations of Brostow and our proposed model as a function of time.