Drag reduction in flow: Review of applications, mechanism and prediction

Drag reduction (DR) agents are used at very low concentrations to accelerate significantly the flow in oil pipeline conduits, oil well operations, flood water disposal, fire fighting, field irrigation, transport of suspensions and slurries, sewer systems, water heating and cooling systems, airplane tank filling, marine systems, and biomedical systems including blood flow. DR agents are typically high molecular mass polymers; this review discusses a mechanism explaining how DR occurs using such agents. All pertinent experimental findings are challenged with that mechanism and all are shown to support it. In industrial applications DR agents undergo mechanical degradation in turbulent flow. An equation predicting the degradation as a function of time is presented and successfully confronted with experimental data. Experimental methods of determination of DR are outlined. Finally a connection between DR and flocculation is discussed.