FIRE FIRE FIRE

Fire Model

Changes:

1) Added brown (dead) trees where a fire can only spread to if it if north, east, south, west of it

2) Changed Green(live) trees where a fire can spread to if in all 8 directions

3) Added sliders fire-density, green-tree-density, brown-tree-density

4) Added monitors for green-trees-burned, brown-trees burned, total-trees-burned

5) Added wind factors that can help fires spread faster

To download the source file click here

created with NetLogo

view/download model file: FIRE FIRE FIRE.nlogo

WHAT IS IT? ----------- This project simulates the spread of a fire through a forest. The fire starts on the left edge of the forest, and spreads to neighboring trees. The fire spreads in four directions: north, east, south, and west. The fire can spread in all eight directions if it spreads to a green tree and four directions (north, east, south, and west) if it spreads to a dead (brown) tree. There is no wind in this particular model as it is. So, the fire must have trees along its path in order to advance. That is, the fire cannot skip over an unwooded area (patch), so such a patch blocks the fire's motion in that specific direction The fire's chance of reaching the right edge of the forest depends critically on the density of live(green) and dead(brown) trees in the forest. HOW TO USE IT ------------- Click the SETUP button to set up the trees (green) and fire (red on the left-hand side). Click the GO button to start the simulation. The North_Wind?, South_Wind?, and East_Wind? buttons activate the wind condition factor. When they are turned on, the fire can spread 2 spaces in that direction if there is a green patch The density_fire slider controls the density of the originating fire in the forest. The density_green_trees slider controls the density of the green trees in the forest. The density_brown_trees slider controls the density of the brown trees in the forest. (Note: Changes in the DENSITY slider do not take effect until the next SETUP.) THINGS TO NOTICE ---------------- Set the density of green trees to 20% and the density of brown trees to 10%. At this setting, there is virtually no chance that the fire will reach the right edge of the forest. Set the density of green trees to 50%. At this setting, it is almost certain that the fire will reach the right edge. There is a sharp transition around 38% density. At 38% density, the fire has about a 50/50 chance of reaching the right edge. Also when the east wind is turned on, the fire spreads farther. The south and north winds don't seem to affect the fire as much. The blue "walls" prevent the fire from spreading off the edges of the screen. Because no turtles are moving on the screen, one could say that the motion of the fire is a construction in our mind. This is an example of an emergent phenomena: each tree is either burning or not burning, but these collective local behaviors amount to an overall effect. The effect (moving fire) is created by the local agents (trees, here), even though it is not experienced by the local agents. So is an emergent phenomenon the same as an optical illusion? That is, do you think that the motion of fire is an optical illusion? Is this the same as the illusion of motion running through a sequence of flashing neon lights? If not, why not? Arguably, there is no "thing" running along the neon lights - just lights flashing. So, is fire a "thing" at all? If not, then how can it move? Moreover, how can it burn? NETLOGO FEATURES ----------------- This project uses only patches, no turtles. Green trees use the "neighbors" primitive and brown trees use the "neighbors4" primitive to determine whether any of the surrounding trees are on fire. Notice how the program gradually decreases the patch color of the red patches to achieve the visual effect of burning out. CREDITS AND REFERENCES ---------------------- This model was developed at the MIT Media Lab. See Resnick, M. (1994) "Turtles, Termites and Traffic Jams: Explorations in Massively Parallel Microworlds." Cambridge, Ma: MIT Press. Adapted to StarLogoT, 1997, as part of the Connected Mathematics Project. Adapted to NetLogo, 2000, as part of the Participatory Simulations Project. To refer to this model in academic publications, please use: Wilensky, U. (1998). NetLogo Fire model. http://ccl.northwestern.edu/netlogo/models/Fire. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.