Drop Impact Simulations

Computational fluid dynamics simulations for drop impact studies using the Basilisk C framework.

Basilisk (Required)

First-time install (or reinstall):

curl -sL https://raw.githubusercontent.com/comphy-lab/basilisk-C/main/reset_install_basilisk-ref-locked.sh | bash -s -- --ref=v2026-01-13 --hard

Subsequent runs (reuses existing basilisk/ if same ref):

curl -sL https://raw.githubusercontent.com/comphy-lab/basilisk-C/main/reset_install_basilisk-ref-locked.sh | bash -s -- --ref=v2026-01-13

Note: Replace v2026-01-13 with the latest release tag.

Overview

This repository contains axisymmetric two-phase flow simulations with adaptive mesh refinement for studying drop impact phenomena. The simulations use the Volume-of-Fluid (VOF) method to track the interface between the drop and surrounding fluid, with automatic mesh refinement focused on regions of interest.

Key Features

• Adaptive Mesh Refinement: Quad/octree-based grids with automatic refinement at interfaces and high-velocity regions
• Two-Phase Flow: Volume-of-Fluid (VOF) method with surface tension modeling
• Axisymmetric Formulation: Efficient 2D simulations with cylindrical symmetry
• Modular Architecture: Separated parameter management, geometry initialization, and diagnostics
• HPC Ready: MPI parallel execution support for large-scale simulations
• Case-Based Organization: Automatic folder management with unique case numbers

Quick Start

Single Simulation

# Edit parameters
vim default.params      # Set CaseNo, We, Oh, etc.

# Run simulation (serial)
./runSimulation.sh

# Run with MPI (4 cores)
./runSimulation.sh --mpi

Parameter Sweep

# Configure sweep
vim sweep.params        # Set CASE_START, CASE_END, sweep variables

# Run sweep (serial)
./runParameterSweep.sh

# Run sweep with MPI (4 cores per case)
./runParameterSweep.sh --mpi

Post-processing

# Run post-processing on one or more cases
./runPostProcess-Ncases.sh 1000 1001

# Show available options
./runPostProcess-Ncases.sh --help

Repository Structure

├── src-local/              Modular header files
│   ├── params.h           Parameter structures and parsing
│   ├── geometry.h         Drop geometry and initialization
│   └── diagnostics.h      Statistics and output handling
├── postProcess/           Post-processing tools and visualization
│   ├── getData-generic.c  Field extraction on structured grids
│   ├── getFacet.c        Interface geometry extraction
│   ├── getFootPrint.c    Footprint height analysis
│   ├── getFootPrint.py   Multi-cutoff footprint time-series
│   ├── plotFootPrint.py  Publication-quality footprint plots
│   └── Video-generic.py  Frame-by-frame visualization pipeline
├── simulationCases/       Case-based simulation outputs
│   ├── dropImpact.c      Main simulation case
│   ├── dropImpact_legacy.c  Legacy simulation source
│   └── runSnellius_legacy.sbatch  Legacy batch script
├── runSimulation.sh       Single case runner
├── runParameterSweep.sh   Parameter sweep runner
├── runPostProcess-Ncases.sh Post-process multiple cases
├── runSweepHamilton.sbatch Hamilton batch script
├── runSweepSnellius.sbatch Snellius batch script
├── default.params         Single-case configuration
└── sweep.params           Sweep configuration

Key Parameters

• Weber Number (We): Ratio of inertial to surface tension forces
• Ohnesorge Numbers (Ohd, Ohs): Viscous/surface tension ratios for drop and surrounding phases
• Reynolds Number: Re = √We/Oh
• Maximum Refinement Level: Controls mesh resolution (e.g., level 10 = 1024 cells)
• Domain Size: Computational domain size in drop radii

Requirements

• Basilisk Framework: Install via the ref-locked script above (upstream docs: basilisk.fr)
• MPI (optional): For parallel execution
  • macOS: brew install open-mpi
  • Linux: sudo apt-get install libopenmpi-dev

References

Key Publications

• Sanjay, V. & Lohse, D. (2025). Unifying theory of scaling in drop impact: forces and maximum spreading diameter. Physical Review Letters, 134(10), 104003. DOI

  • Comprehensive scaling theory for drop impact forces and maximum spreading

• Josserand, C. & Thoroddsen, S. T. (2016). Drop impact on a solid surface. Annual Review of Fluid Mechanics, 48, 365-391. DOI

  • Comprehensive review of drop impact phenomena

• Yarin, A. L. (2006). Drop impact dynamics: Splashing, spreading, receding, bouncing.... Annual Review of Fluid Mechanics, 38, 159-192. DOI

  • Classical review of drop impact dynamics

Documentation

This README provides the user-facing overview and usage. Additional details live in the runnable scripts (runSimulation.sh, runParameterSweep.sh) and in the simulation source (simulationCases/dropImpact.c) and headers in src-local/.

License

See LICENSE file for details.

Contributing

Follow the existing code style and keep changes consistent with the repository's structure and scripts.

Contact

For questions or collaboration inquiries, please contact the CoMPhy Lab.