Can FDS Simulate Ignition Caused by Burning Ember Particles?

[FIN-01]

I am trying to develop a FDS model to investigate whether burning ember-like particles can ignite a combustible surface.

In the model:
A particle (FLYING_EMBER) is defined using a layered surface (EMBER_SURF) with pyrolysis properties.
Particles are continuously injected from a burner located above the target.
A combustible surface is located below, with an assigned material and IGNITION_TEMPERATURE.
However, it is not able to achieve ignition of the target surface.

Before proceeding further, I would like to check whether my modelling approach is fundamentally correct for studying ember-induced ignition in FDS.
I have attached the FDS file for reference.

Any insights or suggestions would be greatly appreciated.

ember.txt

[mcgratta]

Keep in mind that FDS will only compute the radiative heat flux from the hot particle to the solid "ground". There is no conduction from sphere to ground, or convection from the hot boundary layer of the particle to the ground. That being said, one thing that you can do to test the model is to create hot particles with a fixed surface temperature and then contain them within a barrier on the ground. The radiative heat flux to the (cold) ground should approach what one would expect from these hot particles assuming that they eventually cover the area completely. That is, the heat flux would approach $\sigma (T_p^4 - T_g^4)$

[FIN-01]

Many thanks for the response.

My original intention was to investigate ignition caused by burning embers landing on a combustible surface.

Based on your explanation, my understanding is that radiative heat transfer from the particles to the surface is considered in FDS, whereas direct conductive heat transfer between particles and the surface is not explicitly modelled.

If that understanding is correct, would it be fair to say that FDS may have limited capability for simulating ember-induced ignition mechanisms that depend on contact heating?

I am studying the ignition of combustible materials resulting from the flying embers. Would there be a more appropriate modelling approach within FDS for this type of problem, or is this outside the intended capability of the particle model?

Thanks again.

[mcgratta]

There is a probabilistic approach in FDS, where ignition is based on a normal distribution. The reason for this is that in most situations, the ember and the surface upon which it lands will be irregularly shaped. I think that going into details of conductive heat transfer might be unwarranted..