CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM

How to use fixedValue for cyclic Patch

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   July 16, 2012, 10:47
Default How to use fixedValue for cyclic Patch
  #1
Senior Member
 
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 108
Rep Power: 5
zxj160 is on a distinguished road
Dear Foamers,

Does anyone has the experience to create a new BC that can use fixedValue for cyclic patch? I find cyclic patches can not accept any other types of BCs. But I want to set fixedValue for the cyclic inlet.

Many thanks,
Jian
zxj160 is offline   Reply With Quote

Old   July 16, 2012, 11:14
Default
  #2
ngj
Senior Member
 
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,619
Rep Power: 25
ngj will become famous soon enoughngj will become famous soon enough
Hi Jian

You have to elaborate a lot more on what you are trying to accomplish, since enforcing a value on the cyclic patch sounds weird to me, however, it should be possible to wrap something up.

Kind regards,

Niels
ngj is offline   Reply With Quote

Old   July 16, 2012, 11:30
Default
  #3
Senior Member
 
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 108
Rep Power: 5
zxj160 is on a distinguished road
Quote:
Originally Posted by ngj View Post
Hi Jian

You have to elaborate a lot more on what you are trying to accomplish, since enforcing a value on the cyclic patch sounds weird to me, however, it should be possible to wrap something up.

Kind regards,

Niels
Dear Niels,

Thanks. I want to set fixedValue and zeroGradient for cyclic inlet and outlet for a passive scalar. Since I define inlet and outlet as cyclic patches in polyMesh, I can not set other types of BC for cyclic inlet/outlet. I am thinking about how to create a new BC which can set other types of BC (e.g. fixedValue and zeroGradient) for cyclic patches.

My best regards,
Jian
zxj160 is offline   Reply With Quote

Old   July 16, 2012, 13:06
Default
  #4
ngj
Senior Member
 
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,619
Rep Power: 25
ngj will become famous soon enoughngj will become famous soon enough
Hi Jian,

I have given it a thought, and without actual knowing what is inside the code, the jumpCyclic condition could potentially work for you.

Nevertheless, you should be really careful about this, because you are going to consider very carefully how the matrix coefficients should look like in your case, since the cyclicity is suddenly an unwanted feature for some of your solution variables, which you be reflected in both the left hand side and right hand side of your matrix system.

Otherwise, you could generate two identical meshes, continuously map the face fluxes from momentum mesh -> passive scalar mesh and have separate boundary types for the second mesh. It is an extremely crude solution and it will consume a lot more memory, however, if that is not a concern of yours, then you should be alright.

Kind regards,

Niels
ngj is offline   Reply With Quote

Old   July 17, 2012, 09:38
Default
  #5
Senior Member
 
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 108
Rep Power: 5
zxj160 is on a distinguished road
Quote:
Originally Posted by ngj View Post
Hi Jian,

I have given it a thought, and without actual knowing what is inside the code, the jumpCyclic condition could potentially work for you.

Nevertheless, you should be really careful about this, because you are going to consider very carefully how the matrix coefficients should look like in your case, since the cyclicity is suddenly an unwanted feature for some of your solution variables, which you be reflected in both the left hand side and right hand side of your matrix system.

Otherwise, you could generate two identical meshes, continuously map the face fluxes from momentum mesh -> passive scalar mesh and have separate boundary types for the second mesh. It is an extremely crude solution and it will consume a lot more memory, however, if that is not a concern of yours, then you should be alright.

Kind regards,

Niels
Dear Niels,

Many thanks for your suggestion. I am still trying to create a new fixedValue suitable for cyclic patches but without success. Is there any tutorial about jumpcyclic BC (or the tutorials using jumpcyclic BC)?

Additionally, I am thinking about how to select the first layer near the cyclic patches and assign value to them artificially. Let the cyclic BC goes, but later change the values near the boundary. Do you have this kind of experience? Or could you give any idea for it?

My best regards,
Jian
zxj160 is offline   Reply With Quote

Old   July 17, 2012, 09:47
Default
  #6
ngj
Senior Member
 
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,619
Rep Power: 25
ngj will become famous soon enoughngj will become famous soon enough
Hi Jian,

Depending on what you are trying to accomplish, then you could also do a directMapped boundary on the inlet for the hydrodynamics (skipping the state of being in cyclic), because that will within a few time steps give a fully developed inlet flow field.

Kind regards,

Niels
ngj is offline   Reply With Quote

Old   July 17, 2012, 10:08
Default
  #7
Senior Member
 
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 108
Rep Power: 5
zxj160 is on a distinguished road
Quote:
Originally Posted by ngj View Post
Hi Jian,

Depending on what you are trying to accomplish, then you could also do a directMapped boundary on the inlet for the hydrodynamics (skipping the state of being in cyclic), because that will within a few time steps give a fully developed inlet flow field.

Kind regards,

Niels
Dear Niels,

Thanks. I have tried the directMapped BC. But in my case, the pressure drop is through the domain to drive the flow. I use zeroGradient on the outlet and mapped outlet to inlet for pressure. I find the results of pressure increasing so rapidly with running time (from the order of 0.001 to 100). And it is different with the results for cyclic case without passive scalar.

What's the differences between the cyclic and directMapped BC? If a variable is cyclic, when I use directMapped BC, then what kinds of BC should I use for the outlet in order to be similar to cyclic (especially for pressure)?

Best regards,
Jian
zxj160 is offline   Reply With Quote

Old   July 17, 2012, 13:48
Default
  #8
ngj
Senior Member
 
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,619
Rep Power: 25
ngj will become famous soon enoughngj will become famous soon enough
Well, I have typically used directMapped for velocity at the inlet with a zeroGradient on the pressure on the inlet, so I am not quite sure if I can give you any useful advice.

So, I will return to the original advice and look into what is happening in constrained/jumpCyclic and the constructable class derived/fan. This could shed some light onto what is needed.

Kind regards,

Niels
ngj is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Air Conditioned room groovyBC Sebaj OpenFOAM 7 October 31, 2012 15:16
Using starToFoam clo OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 33 September 26, 2012 04:04
CheckMeshbs errors ivanyao OpenFOAM Running, Solving & CFD 2 March 11, 2009 03:34
Import gmsh msh to Foam adorean Open Source Meshers: Gmsh, Netgen, CGNS, ... 24 April 27, 2005 08:19
Multicomponent fluid Andrea CFX 2 October 11, 2004 05:12


All times are GMT -4. The time now is 18:20.