SimScale CAE Forum

Divergent flow, unsure why, no flow lines ect

im trying to analyse the airflow through a 3d printer part cooling fan, i have set the base of the fan as inlet, the hot end and part and buoild plate as non slip walls and the surrounding boxes as pressure outlets yet i seem to have a divergeant flow and now useable flow or data info, any guidance that can be lent would be appreciated

insidentally am mesuring forces on the hot end and part seperatly to determine which puts maximum airflow on the part and not on the nozzle

@Lemlurker can you please share a project link?


I think the first thing to check here is the mesh, there is a hole in the plate where the nozzle appears to touch it. Refining surfaces here should do the trick.

Secondly, the pressure outlets allow air out. However, the direction of flow is actually more along the x-direction. This means that a flow will be induced and therefore will have to go both in and out of the boundaries. This can be achieved with the custom inlet-outlet condition. This might take a few attempts. Alternately, we could increase the bounding box size to encompass the setup, simulating the printer kinda in a big room.

Let me know how it goes,

1 Like

the hole is where the nozzle and the cube are close enough that the meshing solcver links them, would increasing resolution helpp? as for outlet would seeing them as walls with a single outlet not have too much of an effect of the results?

Hi yes increasing the refinement level will improve this, it might be good to increase the level for all surfaces of the part.

What I meant was to change the walls you have currently defined to either inlet-outlet or increase the box and enclose it (giving the same sort of scenario) the second on one won’t work that well however if you add a thermal solver and run as a steady state. There are many ways you could set this up but I don’t think the inlet-outlet method you should at least attempt.

The docs provide a good explanation on inlet-outlets.

Kind regards,

I did a quick test and although it didn’t converge (i think with mesh and some playing with numerics it will) it did show the correct physics i.e. air flowing in and out of the boundaries:

Kind regards,

what specfically did you change between mine and yours?