Drop Impact Simulations

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

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

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
├── runSimulation.sh       Single case runner
├── runParameterSweep.sh   Parameter sweep runner
├── 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: Open-source CFD solver (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

Comprehensive documentation is available in CLAUDE.md, including:

• Coding standards and best practices
• Build and compilation instructions
• Simulation physics and numerical methods
• Parameter descriptions and typical values
• Output file formats and visualization

License

See LICENSE file for details.

Contributing

This repository follows the CoMPhy Lab coding standards. See CLAUDE.md for detailed guidelines on:

• Code style (2-space indentation, 80-character lines)
• Naming conventions (snake_case for variables, camelCase for functions)
• Documentation requirements
• Testing procedures

Contact

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