[opm]

Hi,

I try to setup a simple 2D sliding mesh problem (see appended picture of the mesh) with Workbench and fail at properly creating the interface between the rotating and stationary parts. I already searched through the documentation, this forum and the internet for the last two days and didn't find a solution. Maybe I just fail to recognize what the problem really is. So here is what I did so far:

• I created a geometry in Catia consisting of two circular rotating areas with "blade-dummies" and a rectangular stationary area.
• I formed a new part out of the three surface bodies in DM ("Form New Part" command) to get a conformal mesh.
• I named all the boundaries and fluid zones. That's the step where I assume my problem starts. I tried to created interface-"Named Selections" for both surface edges at the connection between the stationary and the rotating part. Ansys than throws an error at me "The mesh file exporter does not support overlapping geometry in named selections. ..."
• If I just leave it that way, start Fluent, setup the problem and start the calculation, the mesh degenerates after a while and I get negative cell volumes (see the two appended figures, before and after the calculation).
• I tried to make a wall Named Selection and rename it to interior in Fluent like it is described in the "Multiple Rotating Reference Frame" tutorial but had the same results.

Does anyone know how to properly setup the problem in WB DM and Meshing to be able to use the "Mesh Interface" dialog in Fluent?

Thank you in advance.
opm

[opm]

Hi again,

I just tried something else. If i skip the following step

> [...]
> I formed a new part out of the three surface bodies in DM
> ("Form New Part" command) to get a conformal mesh.
> [...]

I am able to create Named Selections for both surface edges (rotating and stationary zones). Now I am able to use the interface dialog in Fluent without any further problems and the calculation is running like expected.

Now the question is how to get this working with a conformal mesh. Any ideas?

Greetings,
opm

[PSYMN]

You don't actually need a conformal mesh (shared nodes), you just want an aligned mesh. You can get this by setting a line sizing the same on both sides of the circle. It should work perfectly. (right click on mesh => Insert Sizing, then select the lines...

Another option that I have not tried yet for 2D curve sizing is the "Match" method. I would have used that if this were a 3D problem.

[tallknuseren]

As PSYMN mentioned, you don't even need a conformal mesh to create a mesh interface, interfaces are for connecting domains who touch at non-conformal faces or edges. Create named selections for the touching geometry at both touching bodies, redefine those to "Interface" at boundary conditions, and create interfaces at "Mesh interface".

I'm struggling with rotor stator simulation also. My problem is that there is a jump in both pressure and velocity across the interfaces, but the mass flux seems to match. Unfortunately, I can't show the whole geometry of this problem, but I attach a screenshot of some part of it. Clearly, you can see the jump in velocity at the countour plot. I should mention, that the flow passes through one stator, further through a rotor and then into the last stator. So there is actually two interfaces.

[PSYMN]

That looks like more than a typical interface jump... Are you sure it is just an internal wall? How about the fluid regions? Do they all have the same properties (viscosity, etc?)

[RR2]

I no this thread is a little bit old now, but i have the same problem as meantioned above. I am doing a 3D CFD analysis on a centrifugal pump with an open impeller. I have two domains, one containging the fluid in the impeller (its a little bit larger than the impeller diameter, only to avoid an interface were the blade ends), and one containing the rest. When defining the interface between them i got some problems.

I have tried both ways described above. When I used the "form new part" command in Designmodeler (to get a conformal mesh) and defined the two interface surfaces as named selections in ANSYS meshing i got an error (the same as the thread starter got). I then tried to use the mesh sizing command in Meshing, and since I am working in 3D I defined this as a face sizing. This didnt change the solution at all, i still got interface jump between the cell zones. You guys also meantioned the match command in Meshing, and I have tried it but don't understand how it works.

As you said above I dont need a conformal mesh to avoid this jump, so any help concering the other options would be appreciated!

In FLUENT I define the interface using the mesh interface command, with default settings (i.e. no periodic boundary condition or coupled wall), so maybe there is some problems there to?

Thanks!

/RR2

[RR2]

Anyone? Appreciate all input i can get!

[Maralady]

RR2 I am having the same issues, somehow I think I am close to the solution, I really think that the problem comes from the solid model, If you want to send me a PM to share information, or if you already solved the problem, please your help will be appreciated, I have opened several threats with a similar subject but I don't get an answer from nobody, and I have not been able to find any documentation that says something about how to create the interfaces at the meshing level.

[Ahmed Saeed Mansour]

Originally Posted by PSYMN

You don't actually need a conformal mesh (shared nodes), you just want an aligned mesh. You can get this by setting a line sizing the same on both sides of the circle. It should work perfectly. (right click on mesh => Insert Sizing, then select the lines...

Another option that I have not tried yet for 2D curve sizing is the "Match" method. I would have used that if this were a 3D problem.

How can i define the interfaces for a sliding mesh 3D pump?

[Fadih]

hello guys,

I am trying to simulate a 3D vertical axis wind turbine, and I have been struggling with overlapping mesh at interfaces and can't seem to find a solution for them. I tried using match control but its not possible because ansys cannot match between 2 bodies even the face selected is shared.
does anyone have any clue how to solve the overlapping mesh.
I have attached pics of my model, the turbine rotates ( hence the big cylinder) also the blade rotate around their center relative to the turbine (hence the 3 inner cylinders)

Is their anything I can do to resolve this.
Please help guys.
Thank you

[Ahmed Saeed Mansour]

Dear Fadi, I got the same problem when I tried to generate a mesh for a 3D impeller of a pump. I had an overlapping mesh problem. After watching a specific video on youtube about sharing topology, the mesh had not any problem. Try to share topology of your 3D design because at the case of a 3D assembly, there is a chance for many meshing problems.
https://www.youtube.com/watch?v=4JhDn0V26l0

https://www.youtube.com/results?sear...hared+topology

[Fadih]

Dear ahmed,
thank you for replying, by sharing topology i am letting ansys know that these 2 are in contact without the need to define contact regions but would i still be able to rotate the fluid volumes? any idea on that end?

[Ahmed Saeed Mansour]

Try all the possible solutions because I didn't try the 3D before...So, try to share topology of all the parts of the turbine to become one part and the mesh should be around this part...after this, define the rotor domain and the stator domains..keep trying and I hope this works.

[Ahmed Saeed Mansour]

Check out this tutorial.
http://www.mediafire.com/download/e8....5_L07_SMM.pdf

[Fadih]

thanks alot

[Ahmed Saeed Mansour]

Not at all, Is there any problem now?....you can check out the mixing tank tutorial on youtube. You can treat the turbine as a one part with a cylinder( rotating domain) and the box will be the static domain and no need for 3 cylinders around each airfoil.

[Fadih]

i have done the 2D case and works perfectly, its just the mesh for the 3D model is tricky, i have done shared topolgy as we speak now waiting for fluent to read the case to check if the mesj is overlapping

[Fadih]

there is no overlap anymore i just need to se if fluent still understands that there are interfaces and its not just one part

[Ahmed Saeed Mansour]

Check out these tutorials

http://www.mediafire.com/download/k7...ry_14.5_v1.zip

[Fadih]

thank you for all your help, greatly appreciated