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simulation of free surface of stirred tank using vof

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Old   November 23, 2012, 03:35
Default simulation of free surface of stirred tank using vof
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Hi alls,
I want to simulate free surface of stirred tank.
I've solved my problem but it seems that results are wrong.
System should be stable after a period of time, but did not stable.
I think thak I don’t do a part of problem.
What should I do that I have not done?
Step by step of my problem:
Read msh file
1) Make grid interfaces (rotor-stator interface)
2) Set multiphase model to VOF with default parameters
3) Set K-E with default parameters
4) Copy water-liquid from materials database
5) Define Air as primary phase
6) Define water as secondary phase
7) Operating condition: active gravity and set -9.81 to Z, (0 0 26.5) as reference pressure location
8) Boundary condition:
A) Rotor fluid: whether moving mesh or mrf , 200rpm
B) Rest fluid: stationary
C) Impeller: stationary
D) Shaft: absolute rotational, 200rpm
E) Top of tank: symmetry
F) Tank walls: no slip
10) initialize, init with default parameters
11) Adapt/ region/ (Xmin=-12, Xmax=12) (Ymin=-12, Ymac=12) (Zmin=0, Zmax=21.5)/ mark
12) initialize/ patch/ volume fraction of water in marked zone is set to 1
13) all parameters of solution is default of fluent
14) time step=0.001 or 0.0001
15) iterate
Attached Images
File Type: png stirred tank.png (28.7 KB, 44 views)
File Type: jpg 1.jpg (97.7 KB, 56 views)
File Type: png impeller_2.PNG (34.9 KB, 38 views)
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Old   November 23, 2012, 05:18
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pictures of your weird results?
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Old   November 23, 2012, 06:01
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Quote:
Originally Posted by -mAx- View Post
pictures of your weird results?
they are here: Eulerian–Eulerian coupled with VOF
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Old   November 23, 2012, 06:07
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i would say interfaces issue -- are those spots exactly where interfaces-intersection are ?
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Old   November 23, 2012, 06:13
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Quote:
Originally Posted by -mAx- View Post
i would say interfaces issue -- are those spots exactly where interfaces-intersection are ?
which spots?
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Old   November 23, 2012, 06:21
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the four red you see on each picture...
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Old   November 23, 2012, 06:27
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Quote:
Originally Posted by -mAx- View Post
the four red you see on each picture...
yes, spots and interfaces are overlap.
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Old   November 23, 2012, 07:02
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then here is the issue.
how many interfaces did you define?
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Old   November 23, 2012, 07:15
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Quote:
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then here is the issue.
how many interfaces did you define?
two interface, 1)rotor perimeter 2) part of rest tank that contact with rotor (You said to me earlier )
odel the stirred tank in GAMBIT
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Old   November 23, 2012, 07:19
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I would say 3:
*rotor perimeter
*top cap of rotor
*bottom cap of rotor
No?
Anyway are you dealing with moving mesh? if yes is it moving properly?
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Old   November 23, 2012, 07:26
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Quote:
Originally Posted by -mAx- View Post
I would say 3:
*rotor perimeter
*top cap of rotor
*bottom cap of rotor
No?
Anyway are you dealing with moving mesh? if yes is it moving properly?
Exactly, I've done all these things and moving is proper
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Old   November 23, 2012, 07:44
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Quote:
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Exactly, I've done all these things and moving is proper
Quote:
Originally Posted by jamalf64 View Post
two interface, 1)rotor perimeter 2) part of rest tank that contact with rotor
So 2 or 3 interfaces defined in Fluent?
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Old   November 23, 2012, 07:56
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Quote:
Originally Posted by -mAx- View Post
So 2 or 3 interfaces defined in Fluent?
I defined rotor perimeter, top cap of rotor, bottom cap of rotor as one interface in GAMBIT and every three are defined rotor interface(as one interface) in fluent
Stator interface is defined similar to rotor
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Old   November 23, 2012, 08:02
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Quote:
Originally Posted by jamalf64 View Post
I defined rotor perimeter, top cap of rotor, bottom cap of rotor as one interface in GAMBIT and every three are defined rotor interface(as one interface) in fluent
It is not correct in regards of topology, because for one interface all surfaces should slide on each other

defined in gambit:
top cap rotor as interface 1
top cap stator as interface 2
bottom cap rotor as interface 3
bottom cap stator as interface 4
perimeter rotor as interface 5
perimeter stator as interface 6

Then in fluent:
grid interface A using interfaces 1 & 2
grid interface B using interfaces 3 & 4
grid interface C using interfaces 5 & 6
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Old   November 23, 2012, 08:07
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Quote:
Originally Posted by -mAx- View Post
It is not correct in regards of topology, because for one interface all surfaces should slide on each other

defined in gambit:
top cap rotor as interface 1
top cap stator as interface 2
bottom cap rotor as interface 3
bottom cap stator as interface 4
perimeter rotor as interface 5
perimeter stator as interface 6

Then in fluent:
grid interface A using interfaces 1 & 2
grid interface B using interfaces 3 & 4
grid interface C using interfaces 5 & 6
Thank you so much
I'll do the things you said and report the results to you
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Old   November 23, 2012, 09:26
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Jamal,
also, if you use mrf you don't need any interface!Create interfaces, as explained by max, only if you use sliding mesh.
If you use mrf you have only to define 2 fluid zones (rotor and stator), without interfaces.

EDIT: "if you use mrf you don't need any interface!" --> if you have a conformal mesh

Last edited by ghost82; November 23, 2012 at 09:46.
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Old   November 23, 2012, 09:40
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Quote:
Originally Posted by ghost82 View Post
Jamal,
also, if you use mrf you don't need any interface!Create interfaces, as explained by max, only if you use sliding mesh.
If you use mrf you have only to define 2 fluid zones (rotor and stator), without interfaces.
What if the mesh is not conformal? Whether it is mrf or sliding mesh, interfaces should be defined as mrf can be thought as a special case of sliding mesh.
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Old   November 23, 2012, 09:45
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Quote:
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What if the mesh is not conformal? Whether it is mrf or sliding mesh, interfaces should be defined as mrf can be thought as a special case of sliding mesh.
Yes Far, if you have a non conformal mesh, then interfaces are necessary also for mrf; however, in my cases, if I used mrf, I preferred to not create interfaces, as in post processing some discontinuities may appear on non conformal interfaces, between fluid zones.

Looking at the mesh model, I think it is quite simple to not create interfaces.

Daniele
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Old   November 23, 2012, 09:55
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Quote:
Originally Posted by ghost82 View Post
Yes Far, if you have a non conformal mesh, then interfaces are necessary also for mrf; however, in my cases, if I used mrf, I preferred to not create interfaces, as in post processing some discontinuities may appear on non conformal interfaces, between fluid zones.

Looking at the mesh model, I think it is quite simple to not create interfaces.

Daniele

I agree..... Thats perfect
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Old   November 23, 2012, 09:57
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Thanks all to your responses
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