Synthetic Variable-Wind Plume Micro-Demo

A compact Python demo that visualizes how a continuously released synthetic tracer plume changes shape in a prescribed two-dimensional variable wind field.

The model combines particle advection, random-walk diffusion, eddy/shear flow, density reconstruction, and four-frame visualization. It is intended as a scientific-computing and data-visualization demonstration, not an operational dispersion model.

Key idea

A plume is not shaped by release location alone. Transport direction, diffusion, wind-field variation, eddies, and visualization choices all affect the final output.

This demo makes those assumptions visible in a small reproducible model.

Main figure

The four-frame output shows the synthetic plume at 2, 5, 10, and 15 minutes. Color shows display-scaled relative density, while arrows show local wind direction and relative strength.

What the model does

The script releases particles from a point source at (0, 0), advances them through a two-dimensional velocity field, adds random-walk diffusion, and reconstructs the plume as four smoothed density snapshots.

The wind field combines:

• Base eastward transport
• Crosswind variation
• A localized downrange eddy
• Mild shear
• Weak stochastic velocity perturbations

The density map is built from particle positions with a 2D histogram, Gaussian smoothing, shared percentile normalization, and gamma display scaling. The display scaling helps show faint outer plume structure alongside the brighter core.

Methods demonstrated

• Lagrangian particle advection
• Random-walk diffusion
• Prescribed two-dimensional wind-field construction
• Eddy/shear flow visualization
• Density reconstruction from particle positions
• Gaussian smoothing
• Shared normalization across time snapshots
• Scientific visualization with NumPy and Matplotlib
• Reproducible synthetic-model documentation

Main outputs

Running the script creates:

figures/synthetic_variable_wind_plume_four_frame.png
figures/synthetic_variable_wind_plume_four_frame.pdf
outputs/run_summary.txt

How to run

Install dependencies, then run the script:

pip install -r requirements.txt
python src/variable_wind_plume.py

Model settings

Key settings are defined near the top of src/variable_wind_plume.py:

• Domain: x = -500 to 3500 m, y = -1500 to 1500 m
• Source: (0, 0)
• Timestep: 5 s
• Total simulation time: 15 min
• Snapshots: 2, 5, 10, 15 min
• Release rate: 150 particles per timestep
• Diffusion coefficient: K = 24 m^2/s
• Density display: global percentile normalization plus gamma scaling

Repository structure

synthetic-plume-variable-wind/
├── README.md
├── LICENSE
├── requirements.txt
├── src/
│   └── variable_wind_plume.py
├── figures/
│   ├── synthetic_variable_wind_plume_four_frame.png
│   └── synthetic_variable_wind_plume_four_frame.pdf
└── outputs/
    └── run_summary.txt

Limitations

This is a synthetic visualization demo. It does not model real terrain, atmospheric stability, deposition, chemical behavior, detector response, emergency response, or site-specific meteorology.

The plume should be interpreted as a controlled computational example for understanding advection, diffusion, wind-field structure, and visualization choices.