Review of turbulent drag-reducing flow and heat transferwith additives

Turbulent dragreduction by additives refers to the phenomenon that the turbulentfriction of a liquid flow in a pipe decreases significantly when high molecular polymer or some kinds of surfactant additives are added to the flow. Studies (experimental study,theoretical analysis, numerical simulation and application testsin real systems) over around a half century since its discoveryhave provided much understanding on the turbulent drag reductionphenomenon and its value in applications. Nevertheless, there arestill some aspects which need to be investigated further, forexample, the turbulent drag reduction mechanism. The currentresearch status in the field of turbulent drag-reducing flow andheat transfer with polymer or surfactant additives is reviewed inthis paper. The characteristics of turbulent drag-reducing flowand heat transfer are summarized in the following aspects:properties of turbulent drag reducers, mechanisms of turbulentdrag reduction with additives, mechanisms of convective heattransfer with turbulent drag reduction, and distribution of thevelocity and the heat transfer control in drag-reducing flow.Furthermore, the applications of turbulent drag reducers in theindustrial systems are discussed. Some new insights on themechanism of turbulent drag reduction by additives, mechanism ofconvective heat transfer with drag reduction, are also reviewed.