CFD modeling and analysis of flow development in high-concentration non-Newtonian coal ash slurry pipelines

Pipeline transport is widely adopted for conveying particulate materials because of its operational efficiency, reduced maintenance, and lower environmental impact compared with conventional transportation methods. Among the available techniques, high-concentration slurry disposal (HCSD) systems have gained prominence due to their ability to lower specific energy consumption while minimizing pipeline erosion and particle degradation at elevated solids loading. Despite extensive studies on HCSD systems, the fundamental flow development behavior – particularly the entrance length – remains insufficiently understood. In this work, the entrance length characteristics of HCSD systems are systematically examined using computational fluid dynamics. The influence of key parameters, including slurry concentration, Bingham Reynolds number, and inlet velocity profile, is analyzed in detail. The findings reveal that the entrance length is highly sensitive to the inlet velocity profile, attaining its maximum value for parabolic profiles under laminar flow conditions and the minimum for uniform profiles in the same regime. In contrast, for turbulent flow, the entrance length is observed to be independent of solid concentration across all inlet profiles. Overall, the entrance length is consistently larger in laminar flow than in turbulent flow for high-concentration slurry transport systems.