Pyro trail and quick interaction

[agelosc]

Hi, I'm trying to create a fire on a falling log of wood and I have two questions if someone can help out.

1. The first challenge was to make the fast moving object emit continuously and not stepped. This is well covered in the forums and I've managed to have a smooth emission by using points with trail as my emitter source and/or by adding substeps. However my question is this: What is the difference between the substep attribute on the DOP Network node and the Min&Max Substeps on the pyrosolver? Both seem to improve on the stepped emission issue but they are obviously different solutions. 

2. Even if the emission is fixed the simulation still doesn't look very good because there is a big trail of emission before anything interesting starts to happen. The fuel & temperature fields need a few substeps to interact with each other and the simulation either comes out too violent and fast or too long and big. What I'm looking for is a fire that is closely "attached" to the log but with a relatively constant speed and length, with a small trail. Do you have any advice on achieving something like that?

Thank for your time.

[Andrea]

Hi!

 

1. The difference is that by using the global substeps option on the DOP network you are always using this many substeps. If you use the min and max substeps on the pyro solver the substeps, the substeps are not constant and you will get them when you need them. This decision is not random but based on a condition which is the CFL condition. I can't realy tell you if one is better than the other for the results/quality but using the min&max should be faster in the same conditions because you are not always forcing the simulation to run the maximum amount of substeps.

2. Not really sure if I pictured it correctly in my mind, I should test or at least see it, but try this. Decrease the Ignition Temperature really really low (0.001), burn rate to 0.999/1, fuel inefficiency to 0 and reduce the Flame height which changes how long the flames will stay on the simulation.

Edited June 20, 2019 by Andrea

[agelosc]

1. That's very clear, thank you.

2. That's the settings I've been using, except for Ignition Temperature which I have a negative value but I assume it's the same as a near zero value. Between posting my questions and now I think I've found a solution to my problem. I've created an extended volume around my emitter/geometry with the velocities of the geometry and adding that velocity field into the sim. This "pushes" the fire around the emission in the same direction as the emitter making the fire more "attached" to the log. Velocity emission from the emitter only seems to have an effect around the emission voxels, while this seems to push a larger part of the simulation with it. 

Thank you for your help.