Abstract
Drag reduction was observed in three distinctly different flow systems-dilute polymer solutions, two-phase solid/liquid suspensions, and three-phase immiscible liquid/liquid flow with suspended solids - in relatively large-diameter pipes (0.027, 0.038, and 0.053 m). Galvanized pipes presented a rough wall, while glass provided a smooth wall and allowed for flow visualization. provided a smooth wall and allowed for flow visualization. By drag reduction, we mean that, for the same flow rate, there is less pressure drop per length of pipe than for the base fluid flowing, alone.Three polymers-sodium carboxymethylcellulose (CMC). polyethylene oxide (POLYOX(TM)), and guar gum) (Jaguar(TM)) were mixed with water to form solutions of various concentrations (from 0.001 to 0.3 wt%). Two nominal concentrations (5 to 10%) of silca sand also were suspended with either tap water or some of the polymers. Finally, white mineral oil and either tap water or polymer solutions were tested. Sand also was added to the oil system.Drag reductions of up to almost 80% were obtained for both the polymer systems and the oil system. Sand suspensions had a maximum of about 35% drag reduction in tap water. However, greatest reductions (more than 90% were attained with the polymer/sand suspensionsSince the sand in the polymer solutions reduced the drag even more than the polymers alone, it may be that the drag mechanism is additive and even may be the same type for both polymers and suspensions.Drag reduction occurs in the region near the wall and could occur in an intermediate layer zone that allows an effective slip velocity to result. Polymers showed significant deviation from the Newtonian velocity profiles.Less power was required to pump the polymers than water alone. Viscosity and normal stress data were obtained also.
Introduction
There are many interesting engineering applications of drag-reduction phenomena. For many flow situations in conduits, the use of a drag reduction agent (normally a viscoelastic soluble polymer) increases flow rate for the same pressure drop in diverse systems. Such as storm sewers, drilling operations, fire fighting, irrigation and living systems. External flows can be improved around ships and torpedoes. Proper design of solid/fluid systems to take advantage of the drag reduction associated with suspended solids can be used in transporting coal, raw sewage, and sediment. In two-phase liquid/liquid situations, such as hydraulic fracturing of oil wells and transportation of liquid petroleum. drag reduction associated with annular immiscible or emulsion flow can be used to advantage where exceptionally large reductions in pressure for a given flow rate result for viscous oils and water.To design systems to take advantage of lower energy requirements at the same flow rate, data are necessary (1) from systems large enough that diameter effects are absent, (2) at flow rates of sufficient velocity that the phenomena are present, and (3) on different systems phenomena are present, and (3) on different systems with varying physical properties. Such data re necessary to develop correlations, to understand flow mechanisms, and to develop mathematical models-all of which are necessary to interpolate and extrapolate the data for design of such flow systems. Previously, this type of data has not been available.Drag reductions is defined, at a given flow rate, as the pressure drop for a given system minus the pressure drop pressure drop for a given system minus the pressure drop for the base fluid divided by the pressure drop for the base fluid.In this paper, we report observations of drag-reduction phenomena in three distinctly different flow systems: (1) phenomena in three distinctly different flow systems:single-phase water, oil, and dilute polymer-water solutions;two-phase oil/water, oil/polymer solution, water/sand, and polymer solution/sand; andthree-phase oil/water/sand and oil/polymer solution/sand.
The data were collected in 0.027- and 0.053-m Schedule 40 galvanized pipe and a 0.038-m-ID smooth-wall glass pipe. pipe. SPEJ
P. 663
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