Blender 2.81 (not mantaflow)
This solution works but was probably never designed to work like this, therefore I can't guarantee that it's a stable workflow. It was stable enough when I tested it anyway.
Unfortunately, you should have already baked your smoke simulation using "External", otherwise you'll need to bake it again. Choose a directory for your ...
Smoke seems like the correct medium to display airflow. Since Blenders smoke does not support suction, you'll have to fake the flow using multiple Forcefield.
Model a simplified collider and mark it as a smoke collision object.
Add an emitter which is fitted into the collider.
Add a forcefield to direct the smoke.
If you use multiple forcefield, make sure ...
As far as I know this is fundamentally impossible.
Physics simulations are sequential data, that means each frame depends heavily on the previous one.
To calculate what happens at any given moment you need to know what happened before, so you must have position and status information about every intervening element in the simulation to know where they were ...
Blender 2.82 (Mantaflow)
For Blender 2.82 and Mantaflow this is fairly straight forward. Simply delete the files from the simulation cache which have the frame number in their name that you would like to remove.
The cache directory will contain two subdirectories config and data which contain the per frame simulation files.
The config directory will ...
Set the flow source on the emitter within the domain to Particle System, and select your particle system.
You can then set the size of those particles below. It will always be a spherical inflow shape, it doesn't take in account any object you set as the particle render shape.
I believe you need to increase the volumetrics clipping end distance. It is in the rendering properties (where you choose between Eevee and Cycles) and then in the Volumetrics foldout :
Be aware that the precision of the particles in the simulation may be affected by that setting. If the simulation is taking place far away you can also increase the clip ...
Quickest way I could work out:
Use a 'screw' modifier on a circle, with an animated angle (and an empty to rotate the circle around), then use this as the emitter. You'd probably want to put it inside your torus object and make it not render.
This works in Blender 2.81a (old smoke sim) and Mantaflow (November 26th 2019 build).
here's what it looks like- ...
Sorry, but I'm afraid not with Blender, either in the old Smoke sim or in Mantaflow.
Here's what happens if you attempt to split the frame range-
Fluid sims (in my limited understanding) are based around vector fields, as you can see when you bake they seem to get slower as they progress (and the vector fields become larger and ...
There is a way, but it's rather complicated and it's not based on the smoke simulation engine, therefore it's also inaccurate... But I'll show it anyway :)
Create a particle system on your emitter
First of all, apply rotation and scale to your emitter (Ctrl+A), then add a particle system to it.
Particle systems, especially of the fluid type, are VERY ...
You can insert keyframes for simulation visibility. Toggle the visibility button for the smoke sim to be off at frame 14 then insert keyframe. Then at frame 15 toggle visibility on then insert keyframe. Finally at frame 16, turn it off again and insert keyframe. It should not keep any of the cached data except for that single frame. FYI it will not show up ...