How to model sub-grid scale trees/vegetation in a 5m grid domain?

[HEROISCOMING1]

Hi everyone,

I am currently working on a simulation with a domain size of 200 x 200 cells using a 5m x 5m grid resolution.

I would like to incorporate trees/vegetation into this model domain, but the scale of an individual tree is significantly smaller than the 5m grid size. Since resolving the detailed geometry of individual trees using standard &OBST lines is not feasible at this grid resolution, I am looking for the best practice to account for their effects.

Could you advise on the recommended approach in FDS for sub-grid vegetation?

[mcgratta]

You can use a combination of level set fire front spread with Lagrangian particles that represent tree foliage. The level set approach moves a fire front as a function of wind, terrain, and vegetation type. The particles add fuel and can lead to greater heat release rates than that predicted by using purely a level set approach. You would want to set LEVEL_SET_MODE=4.

[HEROISCOMING1]

I am working on a simulation where the vegetation I am incorporating should not act as fire fuel. Instead, I want to model how trees affect the wind speed.

Could you please advise on how to properly configure this in FDS?

[mcgratta]

"Properly"? You seem to think that this is some well-established practice. It is not. Generally speaking, wind drag caused by vegetation is modeled using Lagrangian particles. The User's Guide contains a section on how one uses Lagrangian particles to represent vegetation. If the tree foliage is not to burn, you need not include pyrolysis parameters. Focus on size and mass per volume.