THE EFFECT OF 

 ADDITIVES ON FLUID FRICTION 



J. W. Hoyt and A. G. Fabula 

 U. S. Naval Ordnance Test Station 

 Pasadena, California 



INTRODUCTION 



It is now well established that very small concentrations of many natural 

 and synthetic high-polymer substances have the property of reducing the turbu- 

 lent friction drag of the liquid in which they are suspended or dissolved. Be- 

 cause of the many immediate possible applications of such an effect, current 

 interest is high. 



The earliest published data showing turbulent-flow friction reductions in 

 dilute polymer solutions appear to be those of B. A. Toms [1] who studied poly- 

 methylmethacrylate in chlorobenzene. Flow of "thickened gasoline" was the 

 subject of a U.S. Patent in 1949 [2]. Work with aqueous solutions of polymers 

 was reported simultaneously by Shaver & Merrill [3] and Dodge & Metzner [4] 

 both of whom used sodium carboxymethylcellulose as the friction-reducing ma- 

 terial. The technique has found commercial use in oil-field applications [5, 6]. 



Because the earlier workers in the field attributed the friction-reduction 

 phenomenon to "non- Newtonian" fluid properties, the term has become synony- 

 mous with the effect. However, one purpose of this paper is to show that the 

 turbulent-friction reduction effect can be observed (indeed, becomes most 

 prominent) at polymer concentrations at which the solutions are Newtonian by 

 conventional viscometry. Further, it will be shown that polymer additives can 

 be effective in reducing the turbulent friction in concentrations of as little as a 

 few weight parts per million (wppm). 



Although the exact mechanism of the effect is not shown, general rules as 

 to the type of material likely to be effective can be developed, and predictions 

 can be made of the maximum polymer effectiveness in several simple flow situ- 

 ations. It is believed that the generalizations formulated here apply to all sol- 

 vent fluids, but the experimental work has concentrated on aqueous solutions. 



EXPERIMENTS WITH ROTATING DISKS 



Simply because the apparatus happened to be on hand, early work in Pasa- 

 dena was performed on a large-scale rotating disk facility. This equipment 

 (Fig. 1) consists of a 3785 liter water tank in which a 45.7 cm diameter risk is 

 rotated by a d-c electricmotor at such a speed that turbulent flow extends over 



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