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Pipeline Dredge Analytical Program with Comparison to Field Data
Abstract
A clear understanding of pipeline dredge production capacity provides dredge operators and dredging project planners with the capability to accurately and effectively determine a project's cost and duration. Dredge pump and pipeline hydraulics coupled with slurry transport principles present a complex and challenging engineering system requiring specialized knowledge and understanding of how the system will operate. This study determines how well the theoretical principles of hydraulics and slurry transport govern the actual pipeline dredging process, compared with dredge pump and pipeline instrumentation data. Results indicate that the delivered pipeline slurry mixture incurred more friction losses during transport than water alone. This study further determines the maximum pumping capability of the dredge pump in terms of its maximum dredging depth and maximum pipeline length. These results determine that the pipeline dredge operated well within its operating limits during the case study. Overall, the comparison between pump and pipeline instrumentation data to the theoretical background formula demonstrates the reasonable effectiveness of applying the theoretical principles into an analytical program to measure and predict dredge performance.
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... Although it is true that the equations implemented in the dredging equipment by Wilson [27] and the analysis made by Miedema et al. [28] provide an adequate level of understanding of a sediment transport system, it is clear that for realistic Reynolds numbers and turbulence, direct numerical solutions (DNS) of this flow will require a computing power far superior to that currently available in the dredging industry. ...
A model has been developed to characterize the cavitation phenomenon in dredging centrifugal pumps. The operating parameters of a cutter type dredger: swing speed, dredging depth, and inclination, impeller rpm, as well as slurry characterizations such as density and velocity, are introduced, to determine how they influence the operation of the dredge pump. The geometric characterization of the hydraulic transport system of the dredger was performed. With the dredge operationaĺs parameters, along with the geometric characterization, the pump is modeled in CFD turbomachinery software. To validate the operational points, the CFD model considers the RNG k-ε model and the cavitating-multiphase flow. Through the central composite experiment design, the operating conditions range of the dredger is determined, in which the pump can operate and cavitate. This allows validating the model for different operational points. Finally, multiple regression shows the influence of each of the variables in the response obtained. Furthermore, the regression allows an understanding that operating conditions of the dredger must be adjusted to mitigate the phenomenon of cavitation in the dredging process. Keywords: Cavitation, Centrifugal pump, CFD, Dredging, Slurry
Early studies of slurry pipeline systems were based on moderate volumetric concentrations of solids (say up to 18%), for which the excess pressure gradient caused by solids is proportional to concentration. Much larger concentrations now coming into common use show more complicated behaviour. An algebraic analysis is developed to determine desirable operating points and associated energy consumption for settling slurries. This deals initially with the simple proportional behaviour, and then is extended to other cases. Comparison is made to recent experiments using highly concentrated settling slurries with various particle gradings. It is found that near-uniform gradings tend to have high frictional losses, while very broad gradings can give rise to energy-efficient transport at high concentrations.