Cant download step-file. University of Bremen strikes back...
- uni_bremen.JPG (38.59 KiB) Viewed 2885 times
VIIC 1:45 modell
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Be nice to others! Respect the FreeCAD code of conduct!
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thschrader
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- Location: Germany
Re: VIIC 1:45 modell
i cannot test the link from the outer space right now.
Does http://.... work instead of https:// ?
Striking back ... It's spelled "nordisch".
Does http://.... work instead of https:// ?
Striking back ... It's spelled "nordisch".
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thschrader
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- Joined: Sat May 20, 2017 12:06 pm
- Location: Germany
Re: VIIC 1:45 modell
Yes, http works. Next problem: I am running on windows.
But I can use bluecfd-core terminal. What must I do to get
a step-file from the tgz?
- unpack_tgz.JPG (12.09 KiB) Viewed 2880 times
- bluecfd_core_terminal.JPG (46.94 KiB) Viewed 2880 times
Re: VIIC 1:45 modell
tgz is standard unix format. To uncompress on Windows get something like 7-zip, windows commander or such.
Gurgel will show plenty links on how that might be accomplished.
Gurgel will show plenty links on how that might be accomplished.
Re: VIIC 1:45 modell
Frames 20 to 132 redone. some 40 to go ...
First results of the CFD simulation. Total frontal area of the Sub is approx. 0,5m^2. At 0,1m/s water speed the drag force is ca. 0,164mN and the lift force of the aft rudder at 8.75° down ca. 0,01mN (when i haven't done too many mistakes ....)
So now i need to calculate for various rudder settings to get the thre dimensional field of force for the pitch controller.
The meshing takes about 5 minutes and the calculus 20 seconds.
First results of the CFD simulation. Total frontal area of the Sub is approx. 0,5m^2. At 0,1m/s water speed the drag force is ca. 0,164mN and the lift force of the aft rudder at 8.75° down ca. 0,01mN (when i haven't done too many mistakes ....)
So now i need to calculate for various rudder settings to get the thre dimensional field of force for the pitch controller.
The meshing takes about 5 minutes and the calculus 20 seconds.
- AftRudderDown875Deg01ms.jpg (166.79 KiB) Viewed 2858 times
- DragAftDown875Deg01ms.jpg (180.03 KiB) Viewed 2858 times
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thschrader
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- Location: Germany
Re: VIIC 1:45 modell
Hi hds,
the step file contains more than 1000 parts
A real lofting-orgy...FC needs 10 min to load the step.
Each loft is a shell, but I need solids.
Your drag force of 0,164 mN is far to low. Keep in mind that
openfoam calculates a „normalized“ pressure (pressure divided by density),
You must multiply the paraview pressure by a factor of 1000 (water density).
You can check your results by estimating a plausible drag-coefficient.
For your model you should get a drag-force between 1,5-2,0 N.
the step file contains more than 1000 parts
A real lofting-orgy...FC needs 10 min to load the step.
Each loft is a shell, but I need solids.
Your drag force of 0,164 mN is far to low. Keep in mind that
openfoam calculates a „normalized“ pressure (pressure divided by density),
You must multiply the paraview pressure by a factor of 1000 (water density).
You can check your results by estimating a plausible drag-coefficient.
For your model you should get a drag-force between 1,5-2,0 N.
- drag_force.JPG (65.58 KiB) Viewed 2843 times
- 1000_lofts.JPG (42.98 KiB) Viewed 2843 times
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freecad-heini-1
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Re: VIIC 1:45 modell
Hi Thomas,
please check out if import option Zusammenführung is set on:
- step_import_zusammenfuehren.png (79.67 KiB) Viewed 2830 times
Wilfried
Re: VIIC 1:45 modell
oh, thanks a lot for the hint. When recalculating with "p*1000*Normalize_Z" than the drag force = 3.26N. Makes a lot more sense than micros ....
If you like you can get the *stl file if you are interested in the CFD or the directly Foam files. Maybe something else is wrong in there too.
P.S: Frames recutting finished. Now chemicals part 2.
If you like you can get the *stl file if you are interested in the CFD or the directly Foam files. Maybe something else is wrong in there too.
P.S: Frames recutting finished. Now chemicals part 2.
- viicDragRecalculate.jpg (185.42 KiB) Viewed 2826 times
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thschrader
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- Joined: Sat May 20, 2017 12:06 pm
- Location: Germany
Re: VIIC 1:45 modell
@Wilfried: thanks for the tip.
I enabled "STEP compound merge" in Preferences/Import-Export/step,
but I still have 1000 parts after importing.
EDIT:
@Wilfried: I exported all lofts to brep, now I have 1 part.
But still a 2D-shell.
@hds: a drag of 3,26 N at 0,5m^2 area gives a drag coefficient of 1,3.
Mmmh...could that be plausible for a VIIC-sub? Maybe, it is not
a "real" submarine, it is more like a diving ship. But the drag of 3,26 N
does not match to the pressure scale in your picture. When multiplying
the peak pressure with the water density, you get 0,6*1000=600 N/m^2,
thats to high. In an other pic above you calculated 0,027 normalized pressure,
which gives 0,027*1000=27 N/m^2 real pressure at the bow/tower. That seems ok.
Please check the pressure in the (upstream) free-field (the zone between inlet and boat).
At 0,1 m/s inlet speed and 1,0E-06 m^2/s kinematic viscosity the pressure
should be around 5 N/m^2.
Providing the stl/case files would be nice. I can try a run directly in the
bluecfd-core terminal. But dont expect to much, I run a small laptop,
not a high-end university machine...
I enabled "STEP compound merge" in Preferences/Import-Export/step,
but I still have 1000 parts after importing.
EDIT:
@Wilfried: I exported all lofts to brep, now I have 1 part.
But still a 2D-shell.
@hds: a drag of 3,26 N at 0,5m^2 area gives a drag coefficient of 1,3.
Mmmh...could that be plausible for a VIIC-sub? Maybe, it is not
a "real" submarine, it is more like a diving ship. But the drag of 3,26 N
does not match to the pressure scale in your picture. When multiplying
the peak pressure with the water density, you get 0,6*1000=600 N/m^2,
thats to high. In an other pic above you calculated 0,027 normalized pressure,
which gives 0,027*1000=27 N/m^2 real pressure at the bow/tower. That seems ok.
Please check the pressure in the (upstream) free-field (the zone between inlet and boat).
At 0,1 m/s inlet speed and 1,0E-06 m^2/s kinematic viscosity the pressure
should be around 5 N/m^2.
Providing the stl/case files would be nice. I can try a run directly in the
bluecfd-core terminal. But dont expect to much, I run a small laptop,
not a high-end university machine...
Re: VIIC 1:45 modell
That was the design goal. The subs in those days where seagoing vessels with limited diving capabilities.Maybe, it is not
a "real" submarine, it is more like a diving ship.
The foam case is here.
It takes about 1-2minutes to run on a laptop.