Stratified Three-Phase Waves

A numerical framework for simulating three-phase stratified interfacial flows using the Basilisk flow solver.

Overview

This code simulates three immiscible fluid layers with the following configuration:

• Fluid 1 (bottom): Water (ocean)
• Fluid 2 (middle): Oil layer that forms a precursor film
• Fluid 3 (top): Air

The key feature is that Fluid 2 (oil) always maintains a minimum thickness of one grid cell (when we call it a precursor film, it is the worst case scenario) between Fluids 1 and 3.

Key Files

Core Simulation Files

• stratified.c: Main simulation file that sets up the three-phase flow configuration
• three-phase-stratified.h: Header file implementing the three-phase flow solver with Volume-Of-Fluid method
• reduced-three-phase-stratified.h: Implements reduced gravity formulation for the three-phase system

Post-processing Tools

• getData-threePhase.c: Extracts field data from simulation snapshots
• getFacet-threePhase.c: Extracts interface positions
• Video.py: Python script for visualization and video generation

Key Parameters

The main simulation parameters can be found in stratified.c:

• OhBulk: Ohnesorge number for bulk fluid (water)
• mu21, mu31: Viscosity ratios
• rho21, rho31: Density ratios
• sigma12, sigma23: Surface tension coefficients
• Bo: Bond number
• MAXlevel: Maximum grid refinement level

Implementation Details

The three-phase implementation uses two Volume-Of-Fluid fields:

• f1: Distinguishes between fluids 1+2 (value 1) and fluid 3 (value 0)
• f2: Distinguishes between fluid 1 (value 1) and fluids 2+3 (value 0)

The property indices for each fluid are:

• Fluid 1 (water): f1*f2
• Fluid 2 (oil): f1*(1-f2)
• Fluid 3 (air): 1-f1

Running the Code

1. Compile the main simulation:

• Serial

qcc -O2 -Wall stratified.c -o stratified -lm
./stratified

• Using OpenMP

qcc -O2 -Wall stratified.c -o stratified -lm -fopenmp
export OMP_NUM_THREADS=8
./stratified

Here, 8 is the number of threads to use.

• Using OpenMPI

CC99='mpicc -std=c99' qcc -Wall -O2 -D_MPI=1 -disable-dimensions stratified.c -o stratified -lm 
mpirun -np 8 stratified

Here, 8 is the number of MPI processes to use.

Post processing:

python Video.py --CPUs 4

Here, 4 is the number of processors to use.