I'm looking for a way to let particles enter into a tube from the top and when they reach the bottom they should slow down, be pushed radially outwards and then upwards. See a very crude cross section below.

With a regular force I can get them pushed outwards but is there a way to have sort of a tube shaped force that is stronger the farther you get from the center radially?

enter image description here


1 Answer 1


Turn off gravity for both methods.

Using a curve force

Use multiple emitters on multiple layers. Add a curve force to each layer shaping the path of the particles as desired.

Using physical forces

Force this setup I used Wind forces (for the up and down movement), a point force (to disperse the particles at the bottom and a vortex force on the bottom to stop them from drifting away on the horizontal plane.


The wind forces

Use a smaller wind force to push the particles downward (strength -20) with a narrow falloff (0.8, 1.2).
Use a larger wind force to push the particles upward (strength 10). It will also act in the center (where the particles are supposed to go down), which is why the smaller down force has a larger strength to counteract the upward force.

Outward movement at the bottom

A simple point force at the bottom with a radius of 1 - 2 can push the particles away from the center. Since the continue to drift away from the center, a vortex force can pull them back towards it. Here you need to fine tune the value to stop the particles from not following the desired path.

You can use drag forces to remove the XZ velocities. A drag force in combination with a strong wind force will give you good control and can remove some problematic velocity which has built up.


  • $\begingroup$ Brilliant! That helps a lot! I need to play around more with fall of setting to get the hang of it. $\endgroup$ Mar 4, 2019 at 9:27
  • $\begingroup$ Brilliant! That helps a lot! I need to play around more with fall of setting to get the hang of it. To further complicate things, what if the particles were to enter radially from the top? $\endgroup$ Mar 4, 2019 at 15:46
  • $\begingroup$ I'm not sure if I understand your concern. You can edit your answer to include new content (maybe another illustration). You can then mark another answer as accepted. It sounds like it is a different aspect of your problem though and would be well suited for another question. (you should limit yourself to one question per post, however you can open as many threads as necessary.) $\endgroup$
    – Leander
    Mar 4, 2019 at 15:52

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