Working Parameter Combinations

A subforum specific to the development of the OpenFoam-based workbenches ( Cfd https://github.com/qingfengxia/Cfd and CfdOF https://github.com/jaheyns/CfdOF )

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blindmessenger
Posts: 113
Joined: Mon Dec 03, 2018 3:47 pm

Working Parameter Combinations

Post by blindmessenger »

Hi,

perhaps it would be useful to have a thread which lists meaningful working parameter combinations depending on the Fluid properties?

So anyone who wants to contribute something can add it to this thread...

At the end we could possibly create a flowchart...

Best Regards
blindmessenger
Posts: 113
Joined: Mon Dec 03, 2018 3:47 pm

Re: Working Parameter Combinations

Post by blindmessenger »

9mm Cartridge (Freecad 0.20.01_29410 (Git))

Fluid Properties:
Air

Physics model:
- Time: steady
- Flow: Single phase; incompressible; Viscous: yes
- Turbulance: laminar

Initialise Flow Field:
- Velocity: Potential Flow
- Pressure: Potential Flow

Mesh Parameters:
- Mesh Utility: cfmesh
- Base Element Size: 3mm

Mesh Refinement:
- Surface Refinement
- Relative Element Size: 0,1
- Refinement Thickness: 0,1mm
- Boundary Layers: no

Fluid Boundary:
-Inlet: Uniform Velocity; 800m/s for Ux
-Outlet: Static Pressure
-Wall: Slip inviscid (Frictionless Wall)
-Constraint: Symmetry


Boundarys.png
Boundarys.png (47.74 KiB) Viewed 1341 times


Mesh Results:

It is important to have a good value for the Base ELement Size because this value mainly determines the processing time of the solver. So it's best to keep it as small as possible to get a good result, but still keep it big enough that you can use the solver relatively quickly. So if you have a good value in this case 3mm than you should do Refinement because of this:

Meshresults without Refinement:


Mesh_3mm_without_Refine.png
Mesh_3mm_without_Refine.png (50.08 KiB) Viewed 1341 times


Meshresults with a Refinement of Relative Element Size: 0,5 and Refinement Thickness: 0,5mm


Mesh_3mm_Surfacerefine_0,5_0,5_without_Boundarylayer.png
Mesh_3mm_Surfacerefine_0,5_0,5_without_Boundarylayer.png (234.32 KiB) Viewed 1341 times


Meshresults with a Refinement of Relative Element Size: 0,1 and Refinement Thickness: 0,1mm


Mesh_3mm_Surfacerefine_0,1_0,1_without_Boundarylayer.png
Mesh_3mm_Surfacerefine_0,1_0,1_without_Boundarylayer.png (337.82 KiB) Viewed 1341 times


I didn't see much of a difference between with and without doing Boundarylayers. Maybe someone else can explain that.

So the Results in Paraview look like that:


Paraview.png
Paraview.png (118.51 KiB) Viewed 1341 times

Maybe someone has an idea for a more precise model or extensions that they would like to contribute based on this example.
blindmessenger
Posts: 113
Joined: Mon Dec 03, 2018 3:47 pm

Re: Working Parameter Combinations

Post by blindmessenger »

The cad Model.
Attachments
Cartridge_v1.FCStd
(41.69 KiB) Downloaded 32 times
thschrader
Veteran
Posts: 3129
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: Working Parameter Combinations

Post by thschrader »

Here is my approach:
Cartridge_Hisa.FCStd
(161.03 KiB) Downloaded 32 times
Your 9mm bullet at Ma=0,99, solver Hisa, steady-state ("pseudo-transient"), 1/4 Modell.
Mmmh, no clear shockfront visible. But residuals seems good. Or is it?

2D case with another bullet:
9mmBullet.FCStd
(23.17 KiB) Downloaded 30 times

What about posting an excel-file with running examples?
But where can we put the files in one place?

bullet_Hisa_solver.JPG
bullet_Hisa_solver.JPG (63.38 KiB) Viewed 1295 times
cfdof_examples.JPG
cfdof_examples.JPG (88.08 KiB) Viewed 1295 times
thschrader
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Posts: 3129
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: Working Parameter Combinations

Post by thschrader »

and here with shockfront:
9 mm bullet shooting through pipe at Mach 1,75. mesh still too coarse...
shockfront_pressure.JPG
shockfront_pressure.JPG (22.02 KiB) Viewed 1279 times
blindmessenger
Posts: 113
Joined: Mon Dec 03, 2018 3:47 pm

Re: Working Parameter Combinations

Post by blindmessenger »

Hello thschrader,

a formalized data sheet would be good for each case. And then an attached model... Hmmm...
blindmessenger
Posts: 113
Joined: Mon Dec 03, 2018 3:47 pm

Re: Working Parameter Combinations

Post by blindmessenger »

This is what it could look like:



Parameter.png
Parameter.png (132.22 KiB) Viewed 1209 times


If someone wants to change something on the wpc-datasheet, send me a message and I would unprotect the sheet.
Attachments
CFDOF-Working Parameter Combinations_v0.1.xlsx
(14.32 KiB) Downloaded 38 times
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