VIIC 1:45 modell

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thschrader
Posts: 1202
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: VIIC 1:45 modell

Postby thschrader » Thu Jun 14, 2018 10:23 am

hds wrote:
Thu Jun 14, 2018 6:53 am
You may download the step file here
Have fun.
Cant download step-file. University of Bremen strikes back... :D
uni_bremen.JPG
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hds
Posts: 59
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Re: VIIC 1:45 modell

Postby hds » Thu Jun 14, 2018 10:27 am

i cannot test the link from the outer space right now.

Does http://.... work instead of https:// ?

Striking back ... It's spelled "nordisch".
thschrader
Posts: 1202
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: VIIC 1:45 modell

Postby thschrader » Thu Jun 14, 2018 10:38 am

hds wrote:
Thu Jun 14, 2018 10:27 am
i cannot test the link from the outer space right now.

Does http://.... work instead of https:// ?

Striking back ... It's spelled "nordisch".
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?
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hds
Posts: 59
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Re: VIIC 1:45 modell

Postby hds » Thu Jun 14, 2018 10:42 am

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.
hds
Posts: 59
Joined: Tue Feb 14, 2017 8:23 am

Re: VIIC 1:45 modell

Postby hds » Thu Jun 14, 2018 2:47 pm

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.

AftRudderDown875Deg01ms.jpg
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DragAftDown875Deg01ms.jpg
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thschrader
Posts: 1202
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: VIIC 1:45 modell

Postby thschrader » Thu Jun 14, 2018 6:34 pm

Hi hds,
the step file contains more than 1000 parts :shock:
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
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1000_lofts.JPG
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freecad-heini-1
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Re: VIIC 1:45 modell

Postby freecad-heini-1 » Thu Jun 14, 2018 7:49 pm

thschrader wrote:
Thu Jun 14, 2018 6:34 pm
Hi hds,
the step file contains more than 1000 parts :shock:
Hi Thomas,
please check out if import option Zusammenführung is set on:
step_import_zusammenfuehren.png
step_import_zusammenfuehren.png (79.67 KiB) Viewed 333 times
Best regards
Wilfried
hds
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Joined: Tue Feb 14, 2017 8:23 am

Re: VIIC 1:45 modell

Postby hds » Thu Jun 14, 2018 7:53 pm

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.
viicDragRecalculate.jpg
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thschrader
Posts: 1202
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Location: Germany

Re: VIIC 1:45 modell

Postby thschrader » Thu Jun 14, 2018 8:51 pm

@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... :)
hds
Posts: 59
Joined: Tue Feb 14, 2017 8:23 am

Re: VIIC 1:45 modell

Postby hds » Fri Jun 15, 2018 6:17 am

Maybe, it is not
a "real" submarine, it is more like a diving ship.
That was the design goal. The subs in those days where seagoing vessels with limited diving capabilities.
The foam case is here.

It takes about 1-2minutes to run on a laptop.