Hi, I'm currently doing some smoke sims in Houdini using the smoke solver. The final effect is supposed to look like steam pulsating out of a large pipe.

I'm not quite getting the effect I want though.

I have a tube in a SOP which I'm converting into a volume using a Fluid Source. In my DOP I'm scaling the temperature quite a lot to get the steam rising quickly and turbulently.

But I'm getting these pulsating effects; as if the emission is not constant, but emitted in distinct steps.

Raising the amount of timesteps alleviates the problem somewhat; alas the sim time increases a lot. The source is moving too which just makes the problem all the more apparent.

Can someone offer any pointers?
Thanks in Advance

Switching from Projection -> Multigrid to PCG or turning up Multigrid Iterations seems to smooth out the emission a lot.

Pleasure to meet you skurmedel.

Could you please post an image/video of your problem. It might help me solve the problem.

The substep might not be what you are looking for. As for now, i may have an idea. In the fluid source , in the motion blur tab, you can tell houdini to try to blend from frame to frame. This way the emission seem smoother and less choppy? I know Peter Quint did a video for Houdini 12 about that topic.

You should take a look.

http://vimeo.com/38288672 [vimeo.com]

Edit: for clarity and spelling error.

Another way around it could be to Source from a short lifespan particle sim that is over sampled. Seems to be a standard for fast moving missle trails and such to avoid the choppy effect. and if you put a bit of time into the particle sim you get a nice dynamic and interesting source to help get a better pyro sim

Thanks for the replies. Indeed motion blur helped a lot, in combination with more substeps.

The particle sim idea is nice too!