Computational fluid dynamics-based investigation of the formation mechanism and dominant controlling factors of flow resistance in elbow pipe during refined oil transportation

Flow resistance in pipeline elbows is a critical determinant of energy consumption in refined petroleum transportation systems. Understanding the formation mechanism and dominant controlling factors of elbow flow resistance is essential for the optimal design of pipeline infrastructure. However, existing studies have predominantly focused on single-fluid, single-geometry configurations and lack a systematic multi-parameter framework specifically tailored to petroleum pipeline conditions. To address these gaps, this study employs computational fluid dynamics simulation based on the SST k–ω turbulence model to establish a three-dimensional numerical model of elbow flow resistance using 0# diesel as the working fluid representative of actual refined petroleum products. Five governing parameters are systematically investigated: elbow angle (30°–90°), curvature ratio (R/D = 1.0–3.0), pipe diameter (50–90 mm), inlet velocity (0.1–50 m/s, corresponding to Re = 1.60 × 103–8.02 × 105), and ambient temperature (0–50 °C). The novelty of this work lies in three aspects: (1) the identification of three coupled energy dissipation mechanisms—Dean vortex-induced secondary flow momentum loss, flow separation pressure drag due to adverse pressure gradients at the inner wall, and turbulent viscous dissipation driven by velocity gradients—and their Re-dependent relative contributions; (2) a comprehensive multi-parameter resistance framework quantifying the individual and relative effects of all five parameters on both pressure drop (ΔP) and flow non-uniformity coefficient: inlet velocity > curvature ratio > pipe diameter > elbow angle > temperature for ΔP, and curvature ratio > pipe diameter > elbow angle > inlet velocity > temperature for Cv. These findings provide a theoretical foundation for the optimized design of refined petroleum pipeline systems.