Abstract

Many flows of industrial interest contain multiple materials moving and interacting within a pressurized system. Where these materials are moving within a pipe or ducted system, then the materials move as batches with little axial diffusion. Examples including the priming of a sprinkler system as high-pressure water moves through an air-filled network. The practice of sending batches of different materials through the same pipeline is utilized in the oil and gas industry or as a way of moving slurries from quarry to the shipping point. System CFD can be used to model large piping systems and capture both the hydraulic and the dynamic behavior. However, finite volume methods do not preserve the concentration fronts between material slugs due to numerical dispersion. Historically, the Method of Characteristics (MOC) approach has been used in 1D CFD to capture pressure dynamics with low dispersion [2-4]. However, these have typically been limited to fixed grid methods with corresponding limitations in time-step and the range of physical phenomena that can be captured. Meshless or particle-based methods have been available for several years in 2D and 3D CFD [1] but are becoming more common for capturing dynamics within multi-material simulations. This paper demonstrates a new approach to modelling pipe and duct flows within a System CFD framework that takes ideas from both 3D CFD and 1D MOC methods to model multi-material flows that preserve fronts and minimize numerical dispersion. The method tracks “particles” in the flow and solves the 1D-flow equation in the fluid reference fame. A particle re-positioning algorithm is used to handle particles leaving the domain and ensures a minimum loss in fidelity by trapping key features between particles. The paper will demonstrate that a particle-based approach, implemented within the Simcenter Flomaster system CFD tool, can be used to model a variety of physical scenarios that are not possible using traditional system CFD approaches including: Batched slurry flows; Oscillating column in a cavitating vertical pipe; and Pipette flows. The paper will further demonstrate that the approach can be used with a wide range of fluid types including liquids, gases and Non-Newtonian materials. References [1] Liu, GR and Gu, YT, “An Introduction to Meshfree Methods and Their Programming”, Springer, 2005. [2] Hunt, DL, et al, “How To - Model Fluid Flow Systems: Computational Fluid Dynamics versus Fluid System Simulation”, NAFEMS, 2017 [3] Toro, EF, “Riemann Solvers and Numerical Methods for Fluid Dynamics”, Springer 2009 [4] Chaudhry, M. H. “Applied Hydraulic Transient”, 3rd Edition, Springer, 2014