DRAG REDUCTION BY POLYMERS: A BRIEF REVIEW OF THE HISTORY, RESEARCH PROGRESS, AND PROSPECTS

Researchers have investigated the phenomenon of flow drag reduction by polymers for more than 70 years. A lot of progress has been made on understanding the physical process and its wide range of applications in engineering. There are also unsolved problems related to the mechanism of drag reduction and its degradation, and still new technologies and applications for further research and development. This review first summarizes the history of drag reduction by polymers, focusing on technology development and engineering applications. Then, the research progress on drag reduction by polymer additives and its degradation problem is critically reviewed, with a useful summary and analysis of the various numerical and experimental methods and correlations developed. We discuss the difficulties in understanding the mechanism behind the drag reduction and degradation phenomena and offer some new explanations. Lastly, a few promising research topics for future work are discussed.