Assumptions
In order to model fire flow, certain assumptions had to be made. This is due to the complex nature of fire itself. The base foundation of this project is the Elliptical Fire Theory. Because fire flows in a circle, to incorporate other factors would be a matter of shortening and lengthening the radii based on these factors. By adjusting each radii based on the given variables, a more random fire flow model would result. This would be effective for any two-dimensional model, especially since fire flows only on surface area. This flow pattern could later be adapted for a three dimensional model. From this cornerstone, other assumptions were made about the effects of factors on fire flow. The distinction between the heat flow and fire flow models, an improvement over last year’s project, is an example of this. Though the exact relationship is undefined as of yet, fire is dependent upon heat to determine its flow.

Another founding assumption was that fire cannot exist where there is not ample fuel and heat. If fire encounters an area that cannot be burnt under certain conditions then it will be forced to stop. The other assumptions made by the research team in order to complete the program include: no humidity, no ground duff, wind speed. The team also assumed limited fuel types, and two-dimensional fire flow no precipitation, no convection currents produced by the heat of a fire, and no elevation change. These factors although essential to real-world fire spread, have each been simplified because each is a small piece of a larger picture.
Three-Dimensional Fire Spread

Fire does not move on a single plane, and can move in many different levels of forest, including the ground, small shrubs, and even in the canopy in large fires. Firefighters are most concerned about canopy fires because, once a fire reaches the forest crown, it gains speed and can quickly outrun and outmaneuver even the most experienced of fire fighters. Multi-dimensional fire flow was simplified to a two-dimensional plane. By ignoring the third dimension, gravity’s effect on fire can be simplified and almost ignored.

Precipitation
Precipitation effects fire flow of a forest fire by increasing the fuel wetness, which raises the temperature required to maintain persistent fire. Rain will greatly diminish the strength of a fire. Before a fire starts, precipitation will increase the humidity of the ambient environment and the wetness rating of the fuel types. Each of these variables dampens the likelihood of starting a fire and will decrease the “Fire Danger level” as measured by the United States Forest Service. The only related factor is moisture content of the fuel. If it has rained, then the moisture content can be adjusted likewise.

Fire-Generated Wind Currents
Since heat is a byproduct of fire, the heat generated by a fire causes convection currents in the vicinity of the fire and if the fire gets hot enough, the fire will create its own wind currents. Fire-generated wind is very unpredictable and is an important aspect of any fire program that very few models take into account. Fire-generated wind has been left out of this model as well because of the numerous complex aspects that would be involved in modeling heats effect on air currents and the air currents’ effect on fire flow.

Elevation Change
When on a slope, fire will flow faster uphill, rather than downhill, because more of the heat will rise, which then increases the ambient temperature on that part of the slope, causing the fuels to ignite and burn. Elevation has been excluded from this model because the team was unable to verify how elevation affects a fire in the time available. In order to gain exact verifiable insight into elevation’s effect upon fire, empirical data must be acquired.

Oxygen Modeling
Oxygen is one of the three vital factors involved in producing fire. However, it was decided to leave the oxygen component out because oxygen’s effect upon fire must include the convection from the wind-producing fire.

Humidity
By simplifying humidity, a much more uniform fuel type is created, which allows for more even flow of fire. Humidity can vary greatly throughout a forest, depending on precipitation and proximity to a water source. Humidity effects a fire by raising the ignition temperature of the fuel because the fire must first burn away the moisture before it can successfully ignite the fuel. The solution to this is simplifying the assortment of humid fuels to two kinds: wet and dry fuels. The wet and dry fuels possess different flashpoints and can be manipulated according to environmental factors. For example, the wet and dry fuel rating changes depending on whether it was a wet or dry year or if rain has just fallen upon the forest.

Wind
The programs wind assumption maintains that fire radii are dependent upon wind and its angle and based on vectoring to shorten and lengthen radii on the ellipse. Basically, fire is treated as a vector based upon the spread rate and wind direction and angle.

Ground Duff
Ground duff is the dead material at the bottom of a forest. In a coniferous forest, it is generally pine needles, in a deciduous forest, duff is generally composed of dead leaves and plant matter. It affects a fire by drastically increasing the amount of burnable fuel on the ground level. In the program, ground duff has been simplified along with the fuel types. For example, every cottonwood fuel patch will have the same amount of ground duff.

Numerous Fuel Types
Another basic assumption is that fire has the capacity to spread differentially over different fuel types because of the fuel’s typical surface area and atomic structure. Every tree, shrub, and patch of grass has a different values which determine its specific fuel type. By reducing the amount of fuel types, the program is able to better model a simple forest fire with a few varieties of plants and is, therefore, able to be verified easily.

By simplifying these variables, a basic fire spread model has been created. For a future venture a continuation of this program would include many of these variables, The variables would need to be defined and incorporated to better account for the multitude of factors which make up fire.

Oxygen Modeling
Oxygen is one of the three vital factors involved in producing fire. However, it was decided to leave the oxygen component out because oxygen’s effect upon fire must include the convection from the wind-producing fire.

Wind
The programs wind assumption maintains that fire radii are dependent upon wind and its angle and based on vectoring to shorten and lengthen radii on the ellipse. Basically, fire is treated as a vector based upon the spread rate and wind direction and angle.

By simplifying these variables, a basic fire spread model has been created. For a future venture a continuation of this program would include many of these variables, The variables would need to be defined and incorporated to better account for the multitude of factors which make up fire.

Oxygen Modeling Oxygen is one of the three vital factors involved in producing fire. However, it was decided to leave the oxygen component out because oxygen’s effect upon fire must include the convection from the wind-producing fire.

Wind The programs wind assumption maintains that fire radii are dependent upon wind and its angle and based on vectoring to shorten and lengthen radii on the ellipse. Basically, fire is treated as a vector based upon the spread rate and wind direction and angle.

By simplifying these variables, a basic fire spread model has been created. For a future venture a continuation of this program would include many of these variables, The variables would need to be defined and incorporated to better account for the multitude of factors which make up fire.

Oxygen Modeling
Oxygen is one of the three vital factors involved in producing fire. However, it was decided to leave the oxygen component out because oxygen’s effect upon fire must include the convection from the wind-producing fire.

Wind
The programs wind assumption maintains that fire radii are dependent upon wind and its angle and based on vectoring to shorten and lengthen radii on the ellipse. Basically, fire is treated as a vector based upon the spread rate and wind direction and angle.