Is the spread of fire in grassy forests based only on the Level Set Model?

[COCmasterling]

In the user documentation of FDS, in the wildfire spread chapter, the only fire spread model mentioned seems to be the fire Level Set Model, Particle Model and Boundary Fuel Model are just teaching us how to set up the combustible vegetation, so when simulating the spread of wildfires is it just based on the Level Set Model for spread simulation?

[mcgratta]

You can use any of these methods to similar fire spread. However, the particle method requires grid resolution on the order of 1 m or less, which limits the extent of the domain.

[COCmasterling]

Thank you for your answer, so in the official FDS case 14 Canopy Fire Spread, a boundary fuels model is used for the understory vegetation setup and a Lagrangian particle model is used to represent the trees. May I ask which model is being relied upon in the forward spread of the generated fire front?

[mcgratta]

What is the "official FDS case 14 Canopy Fire Spread". I am not familiar with this case or name.

[COCmasterling]

Sorry, my description may not be very accurate. On page 30 of the FDS Validation Guide document 3.14 tells about this case, in this case I have set up the understory surface vegetation to be represented by a boundary fuels model and the trees by a Lagrangian particles model, so the speed of the fire line spreading forward and the length of the fire line in this case is based on which model? Was the level set model used in this case?

[mcgratta]

The Boundary Fuel Model is largely responsible for the spread, but the HRR of the fire is supplemented by the burning of the particles that represent the tree "crowns". The Level Set Model is not invoked in this case.

[COCmasterling]

Thanks again for your generous guidance. I have some more questions, is the velocity model for simulating wildfire spread in FDS optional? Can I use the particle model, the boundary fuels model, and the level set model all at the same time in one simulation? Can the level set model be used with the other two models?

[mcgratta]

What is the "velocity model"? There is nothing to stop you from using them together, but why would you want to? Generally speaking, you use the level set model at grid resolution for which the other two are not appropriate.

[rmcdermo]

When modeling the Fish Lake, Utah, crown fires (a demo) we had to use LS for the understory otherwise the crown (made of particles from Fast Fuels, that is, theoretically take from actual data, at leas the statistics are) would not burn. So at the moment, this is all research. The particle model, which is supposedly the most "accurate", is not really (at any reasonable resolution). The formulation needs improvement.

[COCmasterling]

Thank you for your answers, they have been very beneficial to me. I have gotten the answers I wanted.