I'm sorry for the vague title. I'm trying to think how to explain what i'm asking.

I have a sphere that I turned into smoke, using the shelf tool “Smoke from Objkect”. This uses an IsoOffset to create a volume out of the sphere, and then it creates a VolumeRamp to create a temperature volume from 0 to 1. For the most part I understand what it is doing.

I have remapped that ramp to be 0 to 0.5, which has the effect I want which is to make that smoke essentially “neutral” where it doesn't rise or fall in the sim. What I want now though is to have a way to make it essentially gain and lose heat a tad in a random fashion so it sort of bobs. I want it to do this essentially as a whole volume, but I DO want some of the structure to vary a bit as it bobs so it doesn't feel solid.

My thought was that I could apply some sort of expression on to the VolumeRamp to give me this effect, but I can't seem to figure it out

This is only like my 3rd day really digging into Houdini so any help would be appreciated.

Ok now i'm seeing that part of my problem is that my temperature field is changing over time as part of the sim, outside of my expressions. I noticed that there is a cooling value, which defaults to 0.9. I tried changing that to 1, thinking that would keep the heat constant but it doesn't. So i'm sort of fighting the sim here.