# How to simulate blustery hot air & cold air in Blender

I want to see the behaviour of hot & cold airs against each each other.

In one experiment, please try cloud particles with hot & cold airs.

In another experiment without clouds, please use colours in airs to illustrate their movements. Red for hot and blue cold, as used in CFD softwares like OpenFOAM.

If possible, how to make hot air lose heat over time. If possible, maths would be appreciated.

Edit- I only want to know how to simulate hot & cold winds - in future, I hope to test them against objects like airplanes, rockets, interiors of machines, etc.

Here is another photo for ideas.

• This question mostly sounds like school assignment (or work) :) First of all, this task - if possible, will be pretty hard and tedious in Blender, taking in account physical correctness. Secondly, tell us what have you tried so far, what are the results, and where exactly you need our help. I don't think that somebody will make the whole thing for you here. – cgslav Sep 26 '18 at 22:19
• This question seem way too broad, and sounds like either a homework complete with direct copy-paste from assignment; or a job request. Could you show us what you've got or what you have tried and where it failed? – Duarte Farrajota Ramos Dec 10 '18 at 16:39
• You need houdini at the core of this. There you can manipulate forces, gas pressure and all you mention. I could show you how to do this on Softimage ICE 1-2-3 but sadly it's EOL. Blender Nodes, could do this to some extent, but will not yield the intended "naturally physical simulation results" you are expecting. Houdini it is then... – Pierre Schiller Dec 10 '18 at 18:34
• As a rough visual you could use a smoke setup; single domain, 2 smoke flow sources one with positive temperature difference one with negative, but as Pierre mentioned above this wouldn't be an accurate simulation. Furthermore I don't think you could render it out properly since the render material is based on the domain not the flow emitters. As such you wouldn't have a clear distinction in the render of the 2 flow systems. You could however screen record the simulation running in material shading which would show smoke based on flow emitters. – Ratt Dec 10 '18 at 19:35
• @Ratt Smoke sim might work if it only need to be approximate. It is possible to extract the heat and velocities from the simulation cache so there should be a way to render. – Rich Sedman Dec 10 '18 at 20:16

1. Make a big cube, go to its properties/physics, and enable smoke. Make it a Domain, set its Border Collisions to Collide All.

2. Make a plane, enable smoke physics, and make it a Flow. This means that it emits smoke. Set the smoke color to blue. Use Initial Velocity, and change Normal to 2.

3. Repeat step 2 for red smoke. Change the temperature of this smoke to 5 or something significantly greater than that of the blue.

4. Go to the Domain's material. The nodes are too complex to describe in words, so here:

Note: In Blender 2.8, we have the Principled Volume shader. You can use that instead of the scatter and absorption nodes.

Now, running the simulation, you should have both red and blue smoke.

I used Ben Belisle's answer and this video to answer this enough.

• Old thread: How can you color smoke based on the smoke’s temperature? blender.stackexchange.com/questions/19474/… – Rita Geraghty Dec 15 '18 at 15:55
• My old thread here might give you ideas: How to create anti-gravity in objects like hot-air balloons. (I’m interested in created hot & cold air) blender.stackexchange.com/questions/116720/… – Rita Geraghty Dec 15 '18 at 15:56
• The hot and cold temperatures mix to make a purple color and mixed temperature. The mixing mixes the temperature and color similarly, so purple things have a temperature between that of the red and blue. – Benjamin Jansen Dec 16 '18 at 20:33

You can simulate a naturally physical simulation of your issue using smoke .

A good answer can be take from blender.stackexchange.com/questions/23802/multiple-smoke-flows-in-one-domain-with-different-colors:

Some keywords for smoke effects are:

color
density
flame
heat *
velocity *


You can create emiters for smoke to create wave of smoke with Particle System.

https://docs.blender.org/manual/en/latest/physics/smoke/introduction.html

It says to

1. Create a Domain Object that defines the bounds of the simulation volume.
2. Define a Flow object or objects which will emit smoke and fire.
3. Set Collision objects to make the smoke interact with objects in the scene.
4. Assign a Volumetric material to the domain object.
5. Save the blend-file.
6. Bake the simulation.

Add a cube encompassing the entire volume that you want the smoke. Remember that it's always smart to apply this scale by Ctrl+A. Go to properties/physics, add smoke, and change it to Domain under the smoke options. There are lots of other settings in the RTFM.

Add a Principled Volume shader to the material for the domain, and delete the diffuse. Turn the density down to 0.

Make another object. Go to properties/physics, enable smoke, and change the type to Flow. Duplicate this object, and make sure that both are in the first Domain object.

Add seperate materials to both Smoke Flow objects. Add a Principled Volume for both, and link it to the volume of the output. Delete the default diffusion shader.

I don't currently have access to a Blender computer, but I have done research and believe that this procedure would work. These are my two cents. I am willing to be corrected.

• That sounds interesting. I will have to do more research. – Rita Geraghty Dec 14 '18 at 18:24