Help on model
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Help on model
Hi,
could anybody take a look at the attched model and give me advice why it doesn't work. It's the first version of a cleaning tray.
On top there is a outlet aswell on the bottom. The inlet is via the 4 nozzles (maybe later on there can be more).
Thx a lot
could anybody take a look at the attched model and give me advice why it doesn't work. It's the first version of a cleaning tray.
On top there is a outlet aswell on the bottom. The inlet is via the 4 nozzles (maybe later on there can be more).
Thx a lot
- Attachments
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- Reduced tank model with nozzle inlet.FCStd
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Re: Help on model
For me your case works.
I changed mesh refinement a little bit, laminar case, single cpu run.
My file: OF-version is bluecfd 2017-2 with
OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.23546 (Git)
Build type: Release
Branch: master
Hash: 6b017f9a16b15b0e628c8d874c4058442dee5548
Python version: 3.6.8
Qt version: 5.12.1
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)
I changed mesh refinement a little bit, laminar case, single cpu run.
My file: OF-version is bluecfd 2017-2 with
OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.23546 (Git)
Build type: Release
Branch: master
Hash: 6b017f9a16b15b0e628c8d874c4058442dee5548
Python version: 3.6.8
Qt version: 5.12.1
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)
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- Veteran
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- Location: Germany
Re: Help on model
Aaah..I forgot:
I dont know if the volume-flow is spread across the 4 inlets or
if it is adressed to each face...
I dont know if the volume-flow is spread across the 4 inlets or
if it is adressed to each face...
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Re: Help on model
- Thx, looks fine. It is meant to be volume flow each face. Must it be corrected ?
- You processed it as a laminar case but isn't the flow through the nozzles turbulent ? Does the laminar model describe the flow near the nozzles correctly ?
- So, I thought maybe it is necessary to define each nozzle as a separate inlet in the model. But your answer tells me it's not, right ?
Could it be done ?
- You processed it as a laminar case but isn't the flow through the nozzles turbulent ? Does the laminar model describe the flow near the nozzles correctly ?
- So, I thought maybe it is necessary to define each nozzle as a separate inlet in the model. But your answer tells me it's not, right ?
Could it be done ?
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- Location: Germany
Re: Help on model
Laminar case: start with the most simple arrangement, even when the flow is turbulent.Sidemountyucatan wrote: ↑Fri Jan 15, 2021 4:30 pm - Thx, looks fine. It is meant to be volume flow each face. Must it be corrected ?
- You processed it as a laminar case but isn't the flow through the nozzles turbulent ? Does the laminar model describe the flow near the nozzles correctly ?
- So, I thought maybe it is necessary to define each nozzle as a separate inlet in the model. But your answer tells me it's not, right ?
Could it be done ?
Volume-flow: after case writing for me it is not clear if the volume flow of 2600 mm^3/s is adressed
to each inlet (==> 2600 mm^3/s at each face) or is it 2600/4 for each face.
So in my opinion it would be better to use 4 separat inlets with a clear definition.
Hope that helps. Weeekend....
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Re: Help on model
One last question to the "Laminar"-calculation mode:
You wrote "Laminar case: start with the most simple arrangement, even when the flow is turbulent." What does it mean specifically ?
I mean, which calculation scheme hides behind this mode ? Are RANS-equation being solved ? How is turbulent viscosity handled ?
I try to understand what the software is doing.
Thx for answer.
You wrote "Laminar case: start with the most simple arrangement, even when the flow is turbulent." What does it mean specifically ?
I mean, which calculation scheme hides behind this mode ? Are RANS-equation being solved ? How is turbulent viscosity handled ?
I try to understand what the software is doing.
Thx for answer.
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Re: Help on model
Starting with the most simple arrangement means that you start with the most simple arrangement .Sidemountyucatan wrote: ↑Mon Jan 18, 2021 7:34 am One last question to the "Laminar"-calculation mode:
You wrote "Laminar case: start with the most simple arrangement, even when the flow is turbulent." What does it mean specifically ?
I mean, which calculation scheme hides behind this mode ? Are RANS-equation being solved ? How is turbulent viscosity handled ?
I try to understand what the software is doing.
Thx for answer.
In your case I would do this:
Setup a laminar case ==> test if meshing works, no boundary elements necessary. Mesh ok? (use "checkMesh"). Does the solver run?
If so, refine your modell ==> setup turbulent case, define boundary-layers. Mesh still ok? Does the solver run?
When the basic setup runs, you can do your parameter study by testing different meshes and/or boundary conditions.
You can compare this with the FEM-wb. Before running a complicated case from scratch, for instance using nonlinearities, it
is better to start with a simple linear problem. If this doesnt work, the rest wont either.
The RANS-equations are only solved when using a turbulence model. For understanding the turbulence model and the
solvers you should have a look at this:
https://www.youtube.com/channel/UCcqQi9 ... oUu8eYaEkg
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Re: Help on model
Hi,
I appreciate the discussion a lot. But maybe we missunderstood each other. What I was asking for is the set of formulas being solved in the "laminar case".
I suppose Navier Stokes equations are solved aswell, right ? Is it kind of DNS ?
But now another point: which further approach would you suggest. Currently the "laminar case" is running and it looks fine. Afterwards I will try a run with k-w-SST. But I guess the error message will show up again. What approach would you use ?
Thx
I appreciate the discussion a lot. But maybe we missunderstood each other. What I was asking for is the set of formulas being solved in the "laminar case".
I suppose Navier Stokes equations are solved aswell, right ? Is it kind of DNS ?
But now another point: which further approach would you suggest. Currently the "laminar case" is running and it looks fine. Afterwards I will try a run with k-w-SST. But I guess the error message will show up again. What approach would you use ?
Thx
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Re: Help on model
You can see the used solvers/gradient schemes in the fvSchemes/fvSolution files in the system folder after case writing.Sidemountyucatan wrote: ↑Tue Jan 19, 2021 12:37 pm I appreciate the discussion a lot. But maybe we missunderstood each other. What I was asking for is the set of formulas being solved in the "laminar case".
I suppose Navier Stokes equations are solved aswell, right ? Is it kind of DNS ?
But now another point: which further approach would you suggest. Currently the "laminar case" is running and it looks fine. Afterwards I will try a run with k-w-SST. But I guess the error message will show up again. What approach would you use ?
In my opinion a problem with your model is the very small inlet compared to the whole fluid domain. I dont know what you
want to calculate, but I would start to check which mesh-refinement is necessary to simulate the correct inflow at the inlet.
If the inflow is wrong, you cant expect a correct simulation in the rest of the domain. Imagine you want to simulate a pipe-flow
with your inlet diameter. You need a much finer mesh. I would do 2 steps.
1. Create a separate model with 1 inlet to clarify which mesh/boundary condition/turbulence setting must be used to get a correct inflow.
2. Transfer the result to your complete model.
Openfoam/the Navier-Stokes-equation can solve the turbulence without using a turbulence model ==> DNS-simulation.
But you need a superfine mesh to resolve the micro-turbulence at sub-millimeter-scales. For a practical use (time!)
with a normal PC that wont work. But...give it a try