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Backstep Flow

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Old   February 24, 2015, 08:01
Default Backstep Flow
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saeedbd
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Hi friends
I have started OpenFOAM recently, so i am beginner in it. now i am trying to solve Backstep Flow but i have some problems in it. in fact, i think the mesh is correct but it does not solve properly. this is my first post in this site, who can help me?

i want to solve it with this condition:
u at the inlet is 1.5
L=30
H=1
h=0.5
different reynolds number but laminar flow,2D,incompressible.
note that the cavity here is just a name and i mean Backstep flow
in addition, i am using icoFoam solver.
i wait for your responses, thank you

look at this one. I made it better in Backstep Flow 2. now, the problem is that there is no logical solution after the initial condition. what do you think?
Attached Images
File Type: jpg Screenshot from 2015-02-24 15:24:58.jpg (39.3 KB, 22 views)
Attached Files
File Type: zip Backstep flow.zip (18.3 KB, 5 views)
File Type: zip Backstep Flow 2.zip (5.6 KB, 4 views)

Last edited by saeedbd; February 24, 2015 at 09:18. Reason: better version of my solution
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Old   February 24, 2015, 10:13
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Thiago Parente
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Hi saeedbd,

Check your blockMeshDict. The way you defined the inlet and outlet patches is not usual. You may want to search in tutorials to find a similar boundary condition and better define yours.
I also suggest you to read (if not yet) the User Guide's Sec. 5.2 Boundaries.

Hope it helps.
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Old   February 24, 2015, 20:10
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Quote:
Originally Posted by thiagopl View Post
Hi saeedbd,

Check your blockMeshDict. The way you defined the inlet and outlet patches is not usual. You may want to search in tutorials to find a similar boundary condition and better define yours.
I also suggest you to read (if not yet) the User Guide's Sec. 5.2 Boundaries.

Hope it helps.
Thank you, that was helpful. you can see my progress in the attachments.
I have another question, help me please if possible:
1. I want to solve "Steady state,laminar" of this problem and as you know the icoFoam solver is for transient problems. I searched for suitable solver but i could not. The simpleFoam solver seems to be helpful but it's code does not written for Backstep flow. what is your tip?
2. I want to implement a Parabolic velocity profile. I read some posts related to this but unfortunately they were a little complex for me could you help me please?
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Old   February 25, 2015, 07:43
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Thiago Parente
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Hi saeedbd,

I don't know what you mean with "code does not written for Backstep flow". The simpleFoam is for incompressible steady-state flows, this is your case right? You can set the flow to laminar in turbulentProperties dictionary (see Lid-driven tutorial).

I've never needed a parabolic profile, so I can't help in this case. :/

If you think you are facing too much problems, try a simpler case, e.g., a steady state laminar flow in a 2D duct. Start with a uniform profile (fixedValue) and see if it reaches a full developed profile (parabolic shape), therefore you can assure your BC's are ok. The next step would be to change the inlet profile and at last to modify the domain to the backstep flow case.
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Old   February 25, 2015, 11:48
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Quote:
Originally Posted by thiagopl View Post
Hi saeedbd,

I don't know what you mean with "code does not written for Backstep flow". The simpleFoam is for incompressible steady-state flows, this is your case right? You can set the flow to laminar in turbulentProperties dictionary (see Lid-driven tutorial).

I've never needed a parabolic profile, so I can't help in this case. :/

If you think you are facing too much problems, try a simpler case, e.g., a steady state laminar flow in a 2D duct. Start with a uniform profile (fixedValue) and see if it reaches a full developed profile (parabolic shape), therefore you can assure your BC's are ok. The next step would be to change the inlet profile and at last to modify the domain to the backstep flow case.
if I say "code does not written for Backstep flow" i mean i have some examples of any solver for instance, for icoFoam i have cavity,elbow,... . for simpleFoam also like this, i have airfoil2D, mixerVessel, motorBike,... . you know what I mean? the cavity problem is like backstep and was available in icoFoam category and I changed some parts and got good results but for unsteady condition because of icoFoam. As I'm a beginner, I think it's hard for me to explain my problem. sorry for that.
I think the boundary conditions in my last files(I uploaded theme here) are OK. Of course you're right and I must study examples of the user guide. Thanks for your tip and now I'm working on simpleFoam.
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