Comparative Study of CFD and LedaFlow Models for Riser-Induced Slug Flow

Abstract

The goal of this study is to compare mainstream Computational Fluid Dynamics (CFD) with the widely used 1D transient model LedaFlow in their ability to predict riser induced slug flow and to determine if it is relevant for the offshore oil and gas industry to consider making the switch from LedaFlow to CFD. Presently, the industry use relatively simple 1D-models, such as LedaFlow, to predict flow patterns in pipelines. The reduction in cost of computational power in recent years have made it relevant to compare the performance of these codes with high fidelity CFD simulations. A laboratory test facility was used to obtain data for pressure and mass flow rates for the two-phase flow of air and water. A benchmark case of slug flow served for evaluation of the numerical models. A 3D unsteady CFD simulation was performed based on Reynolds-Averaged Navier-Stokes (RANS) formulation and the Volume of Fluid (VOF) model using the open-source CFD code OpenFOAM. Unsteady simulations using the commercial 1D LedaFlow solver were performed using the same boundary conditions and fluid properties as the CFD simulation. Both the CFD and LedaFlow model underpredicted the experimentally determined slug frequency by 22% and 16% respectively. Both models predicted a classical blowout, in which the riser is completely evacuated of water, while only a partial evacuation of the riser was observed experimentally. The CFD model had a runtime of 57 h while the LedaFlow model had a runtime of 13 min. It can be concluded that the prediction capabilities of the CFD and LedaFlow models are similar for riser-induced slug flow while the CFD model is much more computational intensive.

A Comparative Numerical Investigation of the Behavior of Two‐Phase Hydrocarbon Flow Phenomena in Horizontal Flowline with Different Turbulence Models Using OpenFOAM

“…There are several existing cases of CFD tools for two‐phase flow analysis in straight pipes, but research is often restricted to either a single‐flow regime or two‐dimensional (2D) analysis 32–35. Furthermore, established solvers in commercial software, namely ANSYS Fluent and ANSYS‐CFX, have been applied mostly for research on multiphase flow 1, 26, 36. OpenFOAM has recently gained a firm grip as a substitute simulation tool for conventional commercial software for modeling the transportation of liquid and gas in the pipeline, on account of its friendly syntax for partial differential equations, no licensing costs, fully documented source code, a broad scope of available solvers, and automatic parallelization capacities 1, 37.…”