Add Wind-Driven Forest Fire example

[liyuezha]

Summary

This PR adds a new model example: Wind-Driven Forest Fire.

Compared to forest fire model which focuses on critical thresholds, this model introduces anisotropy caused by wind. It demonstrates how to implement directional bias in grid-based models and explicitly measures the Rate of Spread (ROS) for both the fire head (downwind) and the flank (crosswind).

Motive

Modeling Anisotropy
The model implements a wind-biased ignition probability formula based on the angle between the wind vector and the neighbor direction:
$$p = p_{\text{spread}} \cdot (1 + \text{strength} \cdot \cos(\theta))$$

Implementation

Instead of just counting "burned trees," this model calculates spatial metrics:

• Head Distance: The furthest distance the fire has traveled downwind.
• Flank Width: The lateral width of the fire scar perpendicular to the wind.
• ROS (Rate of Spread): Real-time calculation of the fire front's speed.

Usage Examples

Additional Notes

[EwoutH]

Cool concept, thanks!

Instead of a complete new model, could we also add a wind argument(s) to the existing model? That can be optionally enabled?