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[ANSYS Meshing] constant nonmanifolds

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Old   August 30, 2022, 05:10
Exclamation constant nonmanifolds
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Michal Pecz
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Greetings
For a long time i was working with autodesk CFD and i have to say, throught all its problems at least it never bitched about mesh. I didnt have to prepare everithing in spaceclaim for it, i just capped it easily at place.
With fluent i killed i lot of time with mesh by itself.
So for my points.

1. is there any way to tell to spaceclaim where are my domain inputs and outputs, without specifically creating them in spaceclaim?
there is that setting during inports, saying if its only the solid domain. But how can i then set borders to create the fluid domain? whole idea of meshing first and asking later is nonsensical form me.
2. I have geometry created from multiple parts. During meshing it gets to constant cycling of joining and unjoinig and arguing about nonmanifold geometry. Same geometry that autodesk never got single problem.

I only want to use fluent because of its good speed ant utilising GPU.
But tutorials never help me with anything, because a)interface changed completely or b) they are automatically guessing i used spaceclaim.

By the way, all geometry is done in autodesk inventor.
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Old   September 16, 2022, 05:02
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I guess i will never know.
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Old   September 16, 2022, 08:42
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Not possible.
If you have a solid domain, you have to create a fluid around it, of inside it. This can be done in Spaceclaim quite easily.

Then pass the fluid domain to the mesher, create boundaries there, different domains, create a mesh and import the fluid in Fluent, or CFX. This is the way fluent and CFX users ave been working for more than 30 years already.

The Autodesk CFD is for people who don't want to spend time on this procedure. It is CFD for dummies, who can get away with less accuracy. The best of both worlds........ does not exists. However, ANSYS is trying to accomplish this using Discovery. But that is even less accurate compared to Autodesk CFD.
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Old   September 16, 2022, 09:05
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Michal Pecz
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So why are there even thoose 2 choices of only fluid, and only solid, if fluent already needs both of them?
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Old   September 16, 2022, 09:25
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What is your actual problem?

Fluent will eat everything
- only solid, if you want to calculate the temperature in a solid by conduction.
- only fluid, if you want to calculate the flow, pressure, temperature etc in the fluid.
- solid and fluid simultaneously, if you need them both. For example if you want to study the temperature at the outside of your solid, depending on the flow inside. You can imagine examples yourself.

So it is flexible, and fit for purpose you want.
In the latter case you need to make sure the fluid and solid are joined accurately in Spaceclaim using Share topology. Then you have 1 mutual surface as interface. If they dont match, you'll have 2 surfaces at the same location. But that is preferred.
In Spaceclaim any volume is just a volume, solid, gas, liquid, what ever you want. There is no difference. In the mesher the same, although you give names to the boundaries, and the volumes, so you can find them easily in Fluent. Only in FLuent you give properties to the volumes.
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Old   September 16, 2022, 09:59
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well, right now its fluent mesher. I rarely got problem with mesh in autodesk CFD, but for some reason ansys found problems in geometry i needed nearly always. Or that boundary conditions arent in solver but in mesher. Or so many tutorials that are in old interface.
autodesk CFD may be for dummies but i find it more intuitional. Only reason i wanted to use fluent is GPU acceleration and ability to mix 2 different fluids.

Learning CFD on your own seems depresingly complicated, especially looking for answers.
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Old   September 16, 2022, 10:32
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Aha, you are using Fluent mesher.........
I thought you were using the ANSYS Workbench Mesher. That is what your title says.
Fluent mesher is very new. Therefore, only few turtorials are present. I never used it, so can't answer questions.
Since it is imbedded in the fluent GUI, You could ask the fluent forum for more help.

I don't like fluent either. It is an old package with more and more so-called" improvements. But the core remains old, unstable, and not intuitively, like you mentioned. I only use it if people ask me to use it. Personally, I like CFX much more.
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