Hello, in my pyro sim i get some picture. What could be the reason of these crosses? Divizion size only?

Disable the christmas tree solver.

Do you have any of the shape options enabled on your pyro solver? Try disabling them, that looks like shredding to me, might also be overly aggressive sharpening.

Otherwise it could be that you're injecting values that are too extreme for pyro to solve in a single time step, so you get artifacts. Try turning down the values on your source volume dop, see if that helps.

Had this with sims at work and even had some of our senior FX guys trying to get to the bottom of it. Never got a definitive answer but felt almost like a combo of substep plus an influence scale creating some artefact that busts up vectors in your vel field. You know It's even present in sidefx default shelf sim if remove the visualisation tweaks and look closely.

I recall some success with alternative advection methods in advanced pyro settings and some tweaks in shading on vel tweaks. Can look tomorrow again if I get a chance what helped clean it up