Uneven velocity profile as inlet

Elm · September 25, 2018, 02:57

Hi Foamers,

i do have an cylindric geometry with some inlet pipes at the bottom (see attachment).
Do you know if there is some inlet boundary conditions to model these pipes or an uneven velocity boundary?

I dont want to mesh all the small pipes, so please help me

(The picture of the pipes is just an example)

hyFoam · October 2, 2018, 15:59

Hi Elm,

Have you considered created two different patches while meshing? You could then use two different fixed values in 0/.

Cheers,
Vincent

piu58 · October 3, 2018, 02:49

You may give the velocity at your patch as nonuniform List<vector> . If you don't made this before I recommend to start with uniform velocity and analyze one of the result files. All you gave compact will be nonuniform there and you may see which velocity belongs to which coordinate.
You have to give a 0 file in the same structure.

Elm · October 5, 2018, 05:18

@hyFoam: Yes, the two patches way is my "dirty" solutions ;-)

@piu58 Thanks for that hint, that seems the perfect solution for me!

Tobi · October 5, 2018, 08:34

Hi,

both ways will work, but I would prefer the first one - building two patches based on the following reason:

If you have two patches, you will catch the circular behavior of the inlets
If you have one patch, you will probably get a uniform mesh at the inlet (depending on the meshing strategy), and therefore, you can apply the velocities only to flat, non-curved faces which might influence your result.

However, personally, two patches do not seem to be a 'dirt' workflow. The way, Piu is explaining would be excellent, if:

The flat/curvature inlets does not influence your solution
You have the center points of the inlet pipes; a small codedFixed boundary condition while reading a file that contains the center while calculating the area of the circles and evaluate the included face centers while applying the velocity field, is beautiful, simple and modifiable

Elm · October 8, 2018, 03:18

Thanks for you detailed answer Tobi!
I misunderstood the solution of hyFoam, i'll try both ideas

September 25, 2018, 02:57	Uneven velocity profile as inlet	#1
Elm New Member Join Date: Jul 2018 Posts: 4 Rep Power: 7	Hi Foamers, i do have an cylindric geometry with some inlet pipes at the bottom (see attachment). Do you know if there is some inlet boundary conditions to model these pipes or an uneven velocity boundary? I dont want to mesh all the small pipes, so please help me (The picture of the pipes is just an example)

October 2, 2018, 15:59		#2
hyFoam Member Vince Join Date: Mar 2017 Posts: 45 Rep Power: 9	Hi Elm, Have you considered created two different patches while meshing? You could then use two different fixed values in 0/. Cheers, Vincent Elm likes this.

October 3, 2018, 02:49		#3
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	You may give the velocity at your patch as nonuniform List<vector> . If you don't made this before I recommend to start with uniform velocity and analyze one of the result files. All you gave compact will be nonuniform there and you may see which velocity belongs to which coordinate. You have to give a 0 file in the same structure. atulkjoy and Elm like this. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

October 5, 2018, 08:34		#5
Tobi Super Moderator Tobias Holzmann Join Date: Oct 2010 Location: Tussenhausen Posts: 2,708 Blog Entries: 6 Rep Power: 51	Hi, both ways will work, but I would prefer the first one - building two patches based on the following reason: If you have two patches, you will catch the circular behavior of the inlets If you have one patch, you will probably get a uniform mesh at the inlet (depending on the meshing strategy), and therefore, you can apply the velocities only to flat, non-curved faces which might influence your result. However, personally, two patches do not seem to be a 'dirt' workflow. The way, Piu is explaining would be excellent, if: The flat/curvature inlets does not influence your solution You have the center points of the inlet pipes; a small codedFixed boundary condition while reading a file that contains the center while calculating the area of the circles and evaluate the included face centers while applying the velocity field, is beautiful, simple and modifiable piu58 and Elm like this. __________________ Keep foaming, Tobias Holzmann

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October 5, 2018, 05:18		#4
Elm New Member Join Date: Jul 2018 Posts: 4 Rep Power: 7	@hyFoam: Yes, the two patches way is my "dirty" solutions ;-) @piu58 Thanks for that hint, that seems the perfect solution for me!

October 8, 2018, 03:18		#6
Elm New Member Join Date: Jul 2018 Posts: 4 Rep Power: 7	Thanks for you detailed answer Tobi! I misunderstood the solution of hyFoam, i'll try both ideas