Abstract

A literature survey of the published work on drag reduction by Drag Reducing Agent (DRA) in two-phase flow is reviewed. Characteristics of the two-phase flow with drag reducing additives are described and the research approaches and methodology concerning drag reduction with additives in multiphase flow is introduced. Suggested mechanisms for drag reduction phenomena and procedure in two-phase flow are discussed. Some of the industrial application of the use of drag reducing additives in two-phase flow is explained. Finally, Recommendations, new suggested approaches for future research needs and potential areas that need further research is highlighted.

Introduction

One of the most fascinating advances in single-phase turbulence is the finding that the introduction of small amounts of long-chain polymers into a liquid flow can cause large decreases in the frictional resistance at the wall (Toms, 1948). Several studies with laser doppler velocimetry (Harder and Tiederman, 1991; Wei and Willmarth, 1992; Warholic et al., 1999) have revealed how the turbulence properties differ from those of the solvent.

Warholic and Hanratty used a solution of a co-polymer of polyacrylamide and sodium-acrylate (Percol 727) in water. They realized significant drag-reduction with a concentration as low as 0.25 ppm. The principal effect of the polymer is to reduce Reynolds shear stresses and velocity fluctuations in a direction normal to the wall. Maximum drag-reductions, for which the Reynolds stresses are approximately zero, were observed for polymer concentrations of 13 ppm and 50 ppm.