CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLOW-3D

simulation problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 9, 2010, 02:37
Default simulation problem
  #1
Member
 
bojiezhang
Join Date: Jan 2010
Posts: 64
Rep Power: 7
bojiezhang is on a distinguished road
Preprocessor Messages:
****************************************
** warning - surface area for **
** component 1 is zero **
****************************************

open area mismatch at inter-block boundaries of all blocks
as % of total open area at these mesh boundaries = 8.55612E-11

hello everyone!I have a question about simulation.
first,I do not know what mean for "warning - surface area for component 1 is zero".I set component 1 as a porous component.second ,I have set inter-block by fixed point,why it tells me "open area mismatch ".
so I want to ask if they affact the result and how to solve them?thank you!
bojiezhang is offline   Reply With Quote

Old   April 9, 2010, 05:47
Default
  #2
New Member
 
YongDazztech
Join Date: Sep 2009
Posts: 2
Rep Power: 0
yong is on a distinguished road
Quote:
Originally Posted by bojiezhang View Post
Preprocessor Messages:
****************************************
** warning - surface area for **
** component 1 is zero **
****************************************

open area mismatch at inter-block boundaries of all blocks
as % of total open area at these mesh boundaries = 8.55612E-11

hello everyone!I have a question about simulation.
first,I do not know what mean for "warning - surface area for component 1 is zero".I set component 1 as a porous component.second ,I have set inter-block by fixed point,why it tells me "open area mismatch ".
so I want to ask if they affact the result and how to solve them?thank you!
you should refer this to your respective support in your country.
yong is offline   Reply With Quote

Old   April 10, 2010, 13:13
Default
  #3
Member
 
Yang Yue
Join Date: Feb 2010
Location: Birmingham, UK
Posts: 36
Rep Power: 7
therockyy is on a distinguished road
Quote:
Originally Posted by bojiezhang View Post
Preprocessor Messages:
****************************************
** warning - surface area for **
** component 1 is zero **
****************************************

open area mismatch at inter-block boundaries of all blocks
as % of total open area at these mesh boundaries = 8.55612E-11

hello everyone!I have a question about simulation.
first,I do not know what mean for "warning - surface area for component 1 is zero".I set component 1 as a porous component.second ,I have set inter-block by fixed point,why it tells me "open area mismatch ".
so I want to ask if they affact the result and how to solve them?thank you!
For porous media, when you click "porous properties" under component 1, there will be a list of variables including porosity, X/Y/Z-direction porosity, etc. There is also one blank named "Specific surface area", which has a default value of 0.0. That's the reason why the processor give you such a kind of warning. It won't affect the result.

The open area mismatch like yours won't affect the result either. But try to re-mesh the region will be better. Use uniform mesh size for all mesh blocks or try different mesh size will solve the problem.

Yang
therockyy is offline   Reply With Quote

Old   April 10, 2010, 23:08
Default
  #4
Member
 
bojiezhang
Join Date: Jan 2010
Posts: 64
Rep Power: 7
bojiezhang is on a distinguished road
Quote:
Originally Posted by therockyy View Post
For porous media, when you click "porous properties" under component 1, there will be a list of variables including porosity, X/Y/Z-direction porosity, etc. There is also one blank named "Specific surface area", which has a default value of 0.0. That's the reason why the processor give you such a kind of warning. It won't affect the result.

The open area mismatch like yours won't affect the result either. But try to re-mesh the region will be better. Use uniform mesh size for all mesh blocks or try different mesh size will solve the problem.

Yang
Thank you for your help! But when I try to mesh by cell size or the number of celll,the sofeware will adjust it automatically,so the cell size will become different from what I have meshed.
And the cell of inter-bolck is smaller than the out-block,so they are just connected with some nodes,is it the probem ?
bojiezhang is offline   Reply With Quote

Old   April 11, 2010, 10:00
Default
  #5
Member
 
Yang Yue
Join Date: Feb 2010
Location: Birmingham, UK
Posts: 36
Rep Power: 7
therockyy is on a distinguished road
Quote:
Originally Posted by bojiezhang View Post
Thank you for your help! But when I try to mesh by cell size or the number of celll,the sofeware will adjust it automatically,so the cell size will become different from what I have meshed.
And the cell of inter-bolck is smaller than the out-block,so they are just connected with some nodes,is it the probem ?
Yes, it is a problem. The way I solved this is trying to carefully choose the coordinators of x,y and z direction of the mesh blocks, then choose the appropriate mesh size to make sure the dimension of the mesh block could be divided by the mesh size without remainder. For instance, if I mesh one component in a mesh block with the coordinators of 50mm, 20mm and 10 in 3D, I 'll only choose the mesh cell with size of 5mm, 2mm or even smaller.

When there are two mesh blocks with different mesh size adjacent to each other, I'll try to make sure that the mesh size of one mesh block is the multiply of the other's, like 4mm adhere to 2mm. In this condition, at least nodes of one block will exactly connect with the other one. So, the mismatch is minimized and will keep the influence on the result to a very low level.

My methods sound quite easy but straightforward. I hope it can help you.

Yang
therockyy is offline   Reply With Quote

Old   April 14, 2010, 08:45
Default
  #6
Member
 
bojiezhang
Join Date: Jan 2010
Posts: 64
Rep Power: 7
bojiezhang is on a distinguished road
Quote:
Originally Posted by therockyy View Post
Yes, it is a problem. The way I solved this is trying to carefully choose the coordinators of x,y and z direction of the mesh blocks, then choose the appropriate mesh size to make sure the dimension of the mesh block could be divided by the mesh size without remainder. For instance, if I mesh one component in a mesh block with the coordinators of 50mm, 20mm and 10 in 3D, I 'll only choose the mesh cell with size of 5mm, 2mm or even smaller.

When there are two mesh blocks with different mesh size adjacent to each other, I'll try to make sure that the mesh size of one mesh block is the multiply of the other's, like 4mm adhere to 2mm. In this condition, at least nodes of one block will exactly connect with the other one. So, the mismatch is minimized and will keep the influence on the result to a very low level.

My methods sound quite easy but straightforward. I hope it can help you.

Yang
Thank you very much!I think it is a good idea,and I wil try it later!
bojiezhang 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
problem in tornado simulation with FLUENT, please help Kestas FLUENT 10 April 25, 2012 06:20
Problem restarting a simulation from an intermediate point. sergiorbrett CFX 2 April 21, 2010 17:11
problem of river flow simulation Liu Main CFD Forum 0 May 27, 2004 22:01
2D simulation as boundary condition for 3D problem Jan De smet FLUENT 1 October 11, 2002 02:02
simulation of incineration problem xinxin Main CFD Forum 1 November 27, 1999 17:34


All times are GMT -4. The time now is 17:06.