Drag Reduction in Dredge-Spoil Pipe Flows

The purpose of this study was to determine the preliminary feasibility for reducing the viscous drag in dredge spoil pipe flows by the addition of a high molecular weight, long-chain polyacrylamide polymer. Flow-rate pressure drop tests were conducted on fresh water, dredge spoil samples, clay slurries, and salt water with and without polymer additions. Results demonstrated that as much as 70% drag reduction can be achieved with the addition of a high molecular weight, long-chain polyacrylamide polymer to dredge spoils; and that for a given pressure drop, the flow rate of spoil can be increased. However, the amount of drag reduction decreases and the shear velocity at which 40% drag reduction occurs increases as the total solids content of the spoil increases. Several additional parameters—the effect of particle size, spoil viscosity, pipe diameter, polymer concentration, polymer type, and polymer degradation—need further study.