[Paper Review] Simulations of intermittent two-phase flows in pipes using smoothed particle hydrodynamics

Thomas Douillet-Grellier, Florian De Vuyst+2 more|arXiv (Cornell University)|Apr 18, 2018

Fluid Dynamics Simulations and InteractionsEngineering74 references18 citations

TL;DR

This study demonstrates the application of smoothed particle hydrodynamics (SPH) to simulate intermittent two-phase flows in pipes, using a multiphase SPH formulation with customized inlet/outlet boundary conditions. It successfully reproduces Taitel-Duckler flow regimes, captures slug formation via Kelvin-Helmholtz instability, and models high-density and viscosity ratio flows (up to ~427), confirming SPH's potential for industrial slug flow prediction.

ABSTRACT

Slug flows are a typical intermittent two-phase flow pattern that can occur in submarine pipelines connecting the wells to the production facility and that is known to cause undesired consequences. In this context, computational fluid dynamics appears to be the tool of choice to understand their formation. However, few direct numerical simulations of slug flows are available in the literature, especially using meshless methods which are known to be capable of handling complex problems involving interfaces. In this work, a 2D study of the instability processes leading to the formation of intermittent flows in pipes is conducted using an existing multiphase smoothed particle hydrodynamics formulation associated with inlet and outlet boundary conditions. This paper aims to demonstrate the applicability of smoothed particle hydrodynamics to a given set of close-to-industry cases. First, we check the ability of our implementation to reproduce flow regimes predicted by Taitel and Duckler's flow map. Then, we focus on the transition processes from one flow pattern to the other. Finally, we present the results obtained for more realistic cases with high density and viscosity ratios.

Motivation & Objective

• To assess the capability of smoothed particle hydrodynamics (SPH) in simulating intermittent two-phase flows in pipes, particularly slug flows common in offshore oil and gas pipelines.
• To implement and validate inlet and outlet boundary conditions for multiphase SPH in a 2D pipe geometry.
• To reproduce flow regimes predicted by the Taitel-Duckler flow map and analyze transitions between flow patterns.
• To evaluate SPH performance in high-density and high-viscosity ratio scenarios representative of real industrial conditions.
• To demonstrate the feasibility of SPH as a meshless alternative for modeling complex interfacial dynamics in industrial two-phase flows.

Proposed method

• Adopted a multiphase SPH formulation from prior literature, including surface tension modeling via the continuum surface force model.
• Implemented inlet and outlet boundary conditions tailored for multiphase flows, ensuring mass and momentum conservation at boundaries.
• Used a weakly compressible SPH approach with a cubic spline kernel and artificial viscosity for stability.
• Simulated horizontal and inclined pipe geometries to capture hydrodynamic and terrain-induced slugging mechanisms.
• Applied Fourier analysis to outlet volume fraction time series to extract slug frequency and assess periodicity.
• Validated results against Taitel-Duckler flow map predictions and analyzed transition dynamics between flow regimes.

Experimental results

Research questions

• RQ1 Can SPH accurately reproduce the four main flow regimes (mist, dispersed, intermittent, stratified) predicted by the Taitel-Duckler flow map in a 2D pipe setup?
• RQ2 How do flow patterns transition between each other (e.g., stratified to intermittent) under varying flow conditions in SPH simulations?
• RQ3 To what extent can SPH handle high density and viscosity ratios (up to ~427 and ~32) typical of oil-gas systems?
• RQ4 Can SPH capture the onset and evolution of slug formation via Kelvin-Helmholtz instability in a hydrodynamic slugging scenario?
• RQ5 What is the dominant frequency of slug transit in a riser-like geometry, as inferred from time-series analysis of outlet volume fractions?

Key findings

• SPH successfully reproduced all four flow regimes (mist, dispersed, intermittent, stratified) predicted by the Taitel-Duckler flow map in 2D pipe simulations.
• The formation of slugs was observed to initiate at t = 0.026 s when a wave crest reached the pipe top, triggered by Kelvin-Helmholtz instability.
• In the terrain slugging case, strong oscillations in gas phase volume fraction at the outlet were observed, with a dominant frequency of approximately 226 Hz.
• The Fourier transform of the outlet gas phase volume fraction confirmed periodic slug behavior, supporting the presence of stable slug propagation.
• SPH simulations captured the dynamic evolution of slugs, including length reduction and height increase, eventually occupying the full pipe height.
• The method demonstrated robustness in handling high density and viscosity ratios (up to ~427 and ~32), indicating applicability to realistic industrial conditions.