The Drag Reduction Phenomenon. Observed Characteristics, Improved Agents, and Proposed Mechanisms

Abstract

An overview is presented of experimental and theoretical work conducted at the Naval Research Laboratory on the reduction of hydrodynamic drag. The work establishes the effectiveness of certain chemical additives in reducing drag and defines the character of laminar, transitional, and turbulent flows when such additives are present. A variety of new additives for reducing drag have been developed during the program, and their unique properties are also summarized. Finally, the theoretical work is used as a basis for assessing the relative merits of proposed explanations for the drag reduction phenomenon.

Drag reduction effectiveness and shear stability of polymer-polymer and polymer-fibre mixtures in recirculatory turbulent flow of water

“…Two facts are kept in mind while fabricating the present recirculatory flow set up. It has been reported in the literature [2] that the pipe fittings and bends have deleterious effect on the drag reducing ability of the polymers. Hence in the present system, the fittings and bends have been reduced to a minimum.…”

“…Considerable research work has been done on various aspects of turbulent drag reduction during last twenty years. Excellent reviews on this topic have been written [1][2][3][4] and more and more contributions are being made on various aspects of this interesting phenomenon.…”

Heterogeneous drag reduction in turbulent pipe flows using various injection techniques

“…A widely accepted hypothesis of the mechanism responsible for homogeneous drag reduction is that the microscale eddies in the buffer zone of the turbulent boundary layer are suppressed [21,22]. It is known from flow visualization experiments [23] that the macromolecules affect the sublayer instability which produces jet-like vortices, the so-called bursts, which erupt into the boundary layer and lead to the production of turbulent energy (see also [24]). The frequency of these bursts is reduced by the additives [25].…”

Influence of surfactant on friction pressure drop in a manifold microchannel

“…This theory gives a good explanation that the drag reduction does not exist for laminar flow [11]. It is proposed that the DRA molecules are more active in the buffer zone located between the viscous sub-layer adjacent to the wall surface and the turbulent core of the flow [12].…”