Pipe flow drag reduction effects from carbon nanotube additives

The drag reduction effects of dispersing carbon nanotube (CNT) additives into water–glycerin pipe flow were investigated experimentally. While substantial nanofluid drag reduction from the dilute addition of long and flexible polymers into turbulent flows has been long identified, efforts to demonstrate comparable drag reduction with carbon nanotubes have proved previously unsuccessful. The present results show, for the first time, that CNTs can enhance the drag reducing characteristics of polymer additives. Interestingly, the CNT’s by themselves do not provide drag reduction in the turbulent regime and their additive benefit is lost once the polymers degrade.