[yzyang]

Hey guys, I'm the beginner of ansys fluent and I'm trying to do the simulation regarding flow in a pipe.

The case is that I have a hollow pipe with the solid wall of 1mm, inner diameter of 48.7mm and length of 20cm. Now, a sphere was put in the hollow pipe which located at the center of the pipe (refer to figure) and the fluid will flow over the sphere. Besides that, the pipe is being heated at the same time at temperature of 823K.

The problem that I faced is that I don't know to separate the the fluid flow and the sphere because I can't use the 'cut material' function if I set the solid wall of the pipe and fluid flow as 'add frozen'. Can anybody give me some help in this problem? Thank you very much

[amin.z]

Originally Posted by yzyang

Hey guys, I'm the beginner of ansys fluent and I'm trying to do the simulation regarding flow in a pipe.

The case is that I have a hollow pipe with the solid wall of 1mm, inner diameter of 48.7mm and length of 20cm. Now, a sphere was put in the hollow pipe which located at the center of the pipe (refer to figure) and the fluid will flow over the sphere. Besides that, the pipe is being heated at the same time at temperature of 823K.

The problem that I faced is that I don't know to separate the the fluid flow and the sphere because I can't use the 'cut material' function if I set the solid wall of the pipe and fluid flow as 'add frozen'. Can anybody give me some help in this problem? Thank you very much

hey
Do you want subtract fluid from sphere?

[yzyang]

The sphere is not part of the fluid, it is just in the pipe. I have tried to subtract the sphere from the fluid and preserve the sphere but there is an error shown 'Operation would result in non-manifold bodies'.

[amin.z]

I think you should use:
boolean>subtract
then select fluid as target
and select solid as tool body

[yzyang]

this is exactly the operation that I have failed previously as you can see from the figure. Is that any possible is the problem of my drawing for this case?

[hwet]

you will never be able to mesh a hollow pipe, remember for CFD you need to make a filled pipe so the software can mesh it, for a hollow pipe the software will only mesh the thin wall you made and not its inner area, make a filled pipe and then take out the sphere from it so the sphere will act as a wall inside the pipe then (no material inside the sphere so no mesh and it acts like a wall), hope i make sense

[jrunsten]

I'm willing to make the bet that the sphere and pipe wall are exactly tangent, which would mean that the subtraction would have to create a solid section with zero thickness, which in turn would be impossible to mesh.

Either lower the sphere a bit or elevate it (and maybe put it on a short cylinder or somehting, to make meshing easier in the tight area created)

[yzyang]

Thank you all. I tried to modify my drawing by following all the advice from you all. I extruded a solid wall and fluid with 'add frozen' as operation and formed a sphere with 'add frozen' as operation as well. Then I formed the solid wall and the fluid as a new part so that there are 2 parts and 3 bodies in my drawing. After that, I used the subtract from boolean operation and select fluid as target and sphere as tool body. The boolean operation was done successfully without the error occurred previously.

However, there is a new problem occurred when I tried to do the meshing with the errors were shown in the figure 1 and 2. The meshing that I have set is shown in the left bottom of both of the figure. Is that the meshing that I chosen is incorrect? Then which meshing should I use as I'm not familiar with the meshing setting. Thank you

[hwet]

post a picture of your geometry looking towards the pipe diameter, like ''o'', haha just an example to say what picture I want to see.
Also if you can manage to do it post another picture by change the transparency of the pipe so the sphere is visible inside it from the view you have already posted in the picture. hope i make sense

[yzyang]

hwet, is this the pictures you want me to show you?

[hwet]

I had just asked for these pictures because i suspected that you had not done what I had said in my previous post, go back and read it again and all your issues will be resolved.

[yzyang]

hwet, I have make a filled pipe actually, but I think is not that obvious from the photo uploaded. You can see from the tree outline there. For the sphere, I have used the subtract function from the boolean operation to take out the sphere, but I preserved the sphere because I want to know the wall temperature of the sphere. It is actually no difference in the meshing if I'm not preserve the sphere as I have tried already. So, is that any other problems that I miss?

[hwet]

post ur geometry n mesh file

[yzyang]

hwet, may I know which files you mean?
Is that the one from ''File name>dp0>FFF>DM''?

[yzyang]

I think these are the files you want..if not then tell me again. Thanks a lot!

[hwet]

buddy your mesh n geometry files

[yzyang]

hwet, I only have that two files for the simulation when i save the files and I think there is only geometry file because the meshing cannot be done.

[hwet]

do you use workbench? jus go to file and save and as as design modeler file and for ansys meshing saying as a meshdat file

[yzyang]

hwet, I think this is the file you want

[hwet]

i have looked at your files, the software will just do what you tell it to do, i have sorted out the problem but you must do it yourself go and read my first post again and understand it, you haven't done what i told you to and hence the issue
cheers