[ydima]

Hi,

I am working on a project the past few days. I try to simulate a flow from a syringe into air and on a ground, but I have a lot of issues with the named selections. I indeed never did a work with contact between parts, and I don't really know how to manage them. I have enclosed many pictures to show you my progress.

To clarify, I have sketched the syringe and a ground, and a rectangle (frozen) between them to model air. I want to put velocity as the input parameter at the top of the syringe, and I want the fluid to go out of the syringe at the end (it seems that the flow will not get out here, but I don't know what to do).

I also have the same problem every time: "Model information is incompatible with incoming mesh". I guess it comes from the issues of named selections, especially at the interfaces.

Can someone help me? It would really help me a lot.

Sorry for the language mistakes, I am a French student.

Thank you.

[ngoctm]

Hi,

I think don't understand about the interface in Fluent.

You don't need to create an outlet boundary condition at the contact between syringe and air. This is an interface.

I think you have 2 options for your geometry model: Single-body part and Multi-body part.

Please find an attachment file below for more detail.

Option 1



Option2




Hope this help,

[ydima]

Hi,

Thank you so much for your answer, you cannot imagine how this helps me. However, I did everything like you and I still have the same issue in the results (no velocity in the syringe, and the values seem too high because I chose 0.1m/s for inlet)... Maybe I've done something wrong in the section "mesh interfaces" ? I've never used it before.

Do you know what is the problem now please ?

Thank you again.
Yoann

[ngoctm]

Hi Ydima,

I apologize for being a little confused.

If I understand correctly your problem, it is necessary to re-create the following interfaces.

1. The interface between the syringe and the air domain which the fluid flow passes - outlet.

2. The interface between the syringe and the air which the fluid do not flow passes - wall

In addition, if the fluid in the syringe is a liquid, you will need to modeling with a multiphase model.

Hope this help.

[ydima]

Hi Ngoctm,

I have created both interfaces as you did. Thus, there is no outlet to define in the boundary conditions, right?

I have to work on the multiphase model, because I have never used it before. I will keep you in touch if I have more issues. (I don't work this weekend)

Anyway, thank you so much for the time taken, I am so grateful.

Thank you again.
Yoann

[ngoctm]

Hi Ydima,

yes, that right.

you are welcome.

Best,

[ydima]

Hi Ngoctm,

I worked all day long on the multiphase model, and I finally see some velocity in the syringe AND the air (I deleted the ground btw). However, the results fluctuate a lot with the parameters, and I am not sure about some of them. The main problem is that near the walls of the interface, no matter which results I got, I have a velocity equal to 0 (look at the pictures enclosed). It really seems that something is wrong in this area...

I've chosen a velocity inlet of -0.01 m/s (negative because along -y direction). Actually I am sure to have mistakes with the volume fractions of water and air that I've put as parameters (sometimes it displays me that everything is water or everything is air). As well, I think that there is a problem with the phases, because when I try to show the animation of them, it's like full of primary phase or full of secondary phase (no in between).

Can I send you directly the file of my project? It would actually be easier for both of us. May you give me your mail address by private message?

Thank you again, I am so grateful.
Yoann

[AlexanderZ]

you dont need interfaces

in workbench mesher go to connections -> delete all interfaces
so you will get conform mesh.

Set boundary condition on edge between syringe and air -> interior

best regards

[ydima]

Hi,

Thanks for your help. So I deleted the interfaces and I created 2 new named selections: interior_syr for the 3 edges of the syringe and interior_air for the 3 edges of the air.

However, when I display results, I have the same issue around this area (velocity equal to 0)

Maybe you would like to have my project by email as well?

Yoann

[AlexanderZ]

in workbench geom put all bodies into 1 part
in mesher delete all interfaces
as wall selections you need:
1. Body air
2. body syringe
3. walls of syringe
4. walls of air part

inside Fluent change boundary condition of wall between syringe and air (outlet of syringe) from wall to interior.

best regards

[ydima]

Hi,

I've enclosed some pictures. I created 5 named selections (with the inlet), but I didn't really understand the thing to change in Fluent.

I actually can't select the 3 edges of syringe and the 3 edges of air at the interface for named selections because this leads to an error in the mesh (because I only have one part now). Thus I don't understand how the software is supposed to take the shape of the end of the syringe into account (that would explain the results obtained).

Moreover, how is the software supposed to understand that the syringe is full of water and the air full of air if I only have one part?

Thank you.
Yoann

[AlexanderZ]

on pic 3 and 4 you already have what you need, isn't it?

the only thing to do is to continue the shape of the end of the syringe in air.
Here the most important part is: you dont have wall boundary between the end (outlet) of syringe and air.

use geom on pic2. In geometry module select this two part and click create one part.

In mesher: Delete all interfaces, create mesh -> you will get conform mesh

set all name selections the same way you did on pic 3, but define zone in syringe as syringe (not air) and make unique name of edge on the tip of syringe (outlet). So you will have walls everywhere, but some different name of the tip of syringe

In Fluent go to Boundary conditions, select syringe's tip, and change there the type of Boundary condition to interior


To define water in syringe use PATCH tool.
After initialization push patch (same tab) select here water as variable set 1 as value and select syringe as zone

best regards

[ydima]

Hi!

Thank you very much for explaining the Patch option, I finally have some good results when I display phases (values between 0 and 1 for volume fractions). However, as you can see for the velocity display or phases display, I have a weird issue at the end of the tip. It's like the fluid was leaking at the angle of the tip (if you understand what I mean). I've created the named selection that you asked, but it doesn't change nothing. Moreover, you say that I only have walls, but body_air and body_syr are interior and not walls. When I try to change them as walls in boundary conditions, it creates shadow face zones, but when I simulate it automatically diverges... Do you have an idea on what to do?

By the way, a little question: do I have to create a named selection for the tip of the syringe for the 3 edges (two sides+end) or only the 2 sides? I've tried both but I didn't change a lot so I decided to only choose 2 sides as you can see on a pic.

I'll continue to think about the issue to try to solve it. If you have solutions, I would be very grateful.

Thank you again for your help.
Yoann

[ydima]

When I watch again the simulation, it is actually super weird.. It's not leaking as I believed, but some air is actually going up in the syringe at the angles, and at the end no water is going out of the syringe

When I change the velocity to a positive one (10m/s instead of -10m/s), I
have the issue that water is leaking at the angles, but still nothing is leaking at the end. However, the result is more logic, because the water at the top of the syringe is slowly going down, and the air is not going up in the syringe. But actually I don't understand why? I need a negative velocity to make understand to the software that the velocity is along -y direction right?

Anyway I'm still looking for the issues at the angles and the end of the syringe...

[ydima]

Hi again,

Maybe I didn't understand well your explanation actually. I just changed some named selections by adding the 2 sides of the tip of the syringe in the named selections "walls-syr". I also created a named selection "edge-tip" for the short edge at the end of the syringe and defined it as an interior in boundary conditions, but this actually doesn't change anything in the results obtained (I've tried without this name selection and I got the same thing). However now I get some decent results, as you can see on the pictures.

Yoann

[AlexanderZ]

your domain looks good

best regards

[ydima]

Great, thank you (AlexanderZ and ngoctm) ! I just started the work in 3D, I come back to you if I have major issues

[ydima]

Hi,

I've never done 3D projects before, so I don't really know how to manage named selections here I tried to follow the same approach that the one for 2D (I've cut the air area etc). First thing to remark is that I used the tool called "Fill" to create a volume in the syringe and in the tip, to directly assign the named selection "body_fluid". Thus, I've created one named selection called "body_air", one called "body_fluid", one called "inlet" on the top surface of the volume of fluid, one called "walls_air" on the faces of the cube of air (not in the hole), and one called "walls_syr_tip" simply by picking the 3 parts in the geometry tree.

However I always have errors with the walls between air and the syringe/tip. Indeed, in Fluent, Cell Zone Conditions, "body_air" is detected as a solid, and when I change to fluid, I have a lot of error messages:
"Warning: materials in neighbor cell threads (11 and 9) of
interior zone 2 are of different types (aluminum and air).
This problem MUST be fixed before solving!
Warning: materials in neighbor cell threads (11 and 9) of
interior zone 2 are of different types (aluminum and air).
This problem MUST be fixed before solving!
Warning: materials in neighbor cell threads (11 and 9) of
interior zone 2 are of different types (aluminum and air).
This problem MUST be fixed before solving!
Warning: materials in neighbor cell threads (11 and 9) of
interior zone 2 are of different types (aluminum and air).
This problem MUST be fixed before solving!
Warning: materials in neighbor cell threads (11 and 9) of
interior zone 2 are of different types (aluminum and water-liquid).
This problem MUST be fixed before solving!
Warning: materials in neighbor cell threads (11 and 9) of
interior zone 2 are of different types (aluminum and water-liquid).
This problem MUST be fixed before solving!
Note: Slitting wall zone 2 into a coupled wall.

creating interior-body_air-walls_syr_tip-shadow
Note: Slitting wall zone 4 into a coupled wall.

creating interior-walls_syr_tip-shadow
Initialize using the hybrid initialization method."

I guess that the software doesn't really understand the interface between the syringe/tip and air. Maybe I don't have to create walls in 3D but interfaces? I've never done this before so if someone have some solutions

Thanks!
Yoann

[AlexanderZ]

make a sketch and show clearly, what you've done

best regards

[ydima]

Hi,

Okay so here are some pictures to explain the different parts in the geometry (syringe, tip, air and fluid inside the syringe+tip).

For the air, I zoomed on where I cut.