Investigation of deposition behavior in non-Newtonian oil-wax slurry pipeline transport based on experiment and CFD-CGDEM method

• Non-Newtonian rheology of heavy component blends was characterized. • A CFD-CGDEM model for multiphase non-Newtonian transport was developed. • Flow characteristics of oil-wax slurry mixed transportation are revealed. Blending and transporting bottom sludge from crude oil storage tanks with light oil is one of the primary disposal methods. However, as the blending concentration increases, the non-Newtonian characteristics of the mixture become more pronounced, and the multiphase flow behavior coupled with these rheological features remains insufficiently understood. In this study, the non-Newtonian rheological behavior of wax-particle–laden blended oil was investigated through experiments. A coupled CFD-CGDEM multiphase flow model was developed to simulate the sludge transport process, based on the open-source software OpenFOAM and in-house code XDEM. Results show that the Cross model provides the best fit for the rheological behavior within a blending concentration range of 6% to 30%, with Adjusted-R² values between 0.959 and 0.999. The CFD-CGDEM simulation results were validated against experimental data, demonstrating high accuracy. As flow rate increases, heavy components tend to concentrate in the pipe center, while near-wall concentrations remain lower. Additionally, the number of particles accumulating and settling at the bottom of the pipeline increases rapidly at first and then more gradually with increasing blending concentration. Considering the impact of different coarse-graining factors on computational efficiency and result accuracy, a CG factor of 2 demonstrates better adaptability for numerical simulations.