CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

How to applying surface roughness in Openfoam damBreak?

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

Like Tree4Likes
  • 2 Post By Phicau
  • 1 Post By Phicau
  • 1 Post By mAlletto

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 4, 2018, 19:50
Question How to applying surface roughness in Openfoam damBreak?
  #1
New Member
 
Jesse Cheung
Join Date: Apr 2018
Posts: 18
Rep Power: 4
kcc49 is on a distinguished road
Hello, I am a new OpenFOAM user and currently working on how the effect of surface roughness affecting the impact introduced by dam break.

As a result, I am building a model through using the damBreak in OpenFoam Tutorial. Is there any way to introduce surface roughness into damBreak?

sincerely,
Jesse
kcc49 is offline   Reply With Quote

Old   April 4, 2018, 20:49
Default
  #2
Senior Member
 
Pablo Higuera
Join Date: Jan 2011
Location: Auckland
Posts: 565
Rep Power: 14
Phicau is on a distinguished road
Hi Jesse,

you need to run the case with a turbulence model and specify nutkRoughWallFunction for nut.

Ks is the equivalent grain roughness (Nikuradse) and Cs is a roughness constant, check the details here: https://cpp.openfoam.org/v3/a01666.html#details

All this is put into play in the damBreakWithObstacle tutorial.

Best,

Pablo
aow and saatt like this.
__________________
Check out my new project: olaFlow --> The olaFlow Support Thread
Phicau is online now   Reply With Quote

Old   April 4, 2018, 21:44
Default
  #3
New Member
 
Jesse Cheung
Join Date: Apr 2018
Posts: 18
Rep Power: 4
kcc49 is on a distinguished road
Quote:
Originally Posted by Phicau View Post
Hi Jesse,

you need to run the case with a turbulence model and specify nutkRoughWallFunction for nut.

Ks is the equivalent grain roughness (Nikuradse) and Cs is a roughness constant, check the details here: https://cpp.openfoam.org/v3/a01666.html#details

All this is put into play in the damBreakWithObstacle tutorial.

Best,

Pablo
thanks Pablo for your response!
However, I still not quite sure how to run the case with a turbulence model and specify nutkRoughWallFunction for nut.
Do you mind elaborate more?

Many thanks!
Jesse
kcc49 is offline   Reply With Quote

Old   April 5, 2018, 06:01
Default
  #4
New Member
 
Jesse Cheung
Join Date: Apr 2018
Posts: 18
Rep Power: 4
kcc49 is on a distinguished road
Quote:
Originally Posted by Phicau View Post
Hi Jesse,

you need to run the case with a turbulence model and specify nutkRoughWallFunction for nut.

Ks is the equivalent grain roughness (Nikuradse) and Cs is a roughness constant, check the details here: https://cpp.openfoam.org/v3/a01666.html#details

All this is put into play in the damBreakWithObstacle tutorial.

Best,

Pablo
Hello Pablo,

Does it mean all I need to do is to change the value of Ks and Cs (in bold text) nut file in file 0 in order to control the surface roughness?

Quote:
boundaryField
{
atmosphere
{
type zeroGradient;
}

walls
{
type nutkRoughWallFunction;
Ks uniform 100e-6;
Cs uniform 0.5;

value $internalField;
}
}
kcc49 is offline   Reply With Quote

Old   April 5, 2018, 06:19
Default
  #5
Senior Member
 
Pablo Higuera
Join Date: Jan 2011
Location: Auckland
Posts: 565
Rep Power: 14
Phicau is on a distinguished road
Exactly, select the appropriate values for your case and check damBreakWithObstacle tutorial if you can't make it work at first.

Pablo
kcc49 likes this.
__________________
Check out my new project: olaFlow --> The olaFlow Support Thread
Phicau is online now   Reply With Quote

Old   April 5, 2018, 06:22
Default
  #6
New Member
 
Jesse Cheung
Join Date: Apr 2018
Posts: 18
Rep Power: 4
kcc49 is on a distinguished road
Many thanks for your help!
kcc49 is offline   Reply With Quote

Old   April 5, 2018, 08:41
Default
  #7
New Member
 
Jesse Cheung
Join Date: Apr 2018
Posts: 18
Rep Power: 4
kcc49 is on a distinguished road
Quote:
Originally Posted by Phicau View Post
Exactly, select the appropriate values for your case and check damBreakWithObstacle tutorial if you can't make it work at first.

Pablo
I have another question for building up the case

int the nut file, do i need to include those 'faces' as zeroGradient? see the following quote

Quote:
atmosphere
{
type zeroGradient;
}

wall
{
type zeroGradient;
}

structure
{
type zeroGradient;
}

slope
{
type nutkRoughWallFunction;
Ks uniform 0.05;
Cs uniform 1;
value $internalField;
}
side
{
type empty;
}
kcc49 is offline   Reply With Quote

Old   December 19, 2018, 16:19
Default
  #8
New Member
 
Nicola D'Ettole
Join Date: Nov 2018
Posts: 12
Rep Power: 3
ing.nicola.dettole is on a distinguished road
For velocity , pressure, k, epslion i have to use rough functions ?
ing.nicola.dettole is offline   Reply With Quote

Old   January 16, 2020, 18:15
Default
  #9
New Member
 
Join Date: Nov 2019
Posts: 24
Rep Power: 2
Nic86 is on a distinguished road
Hello. The nutkRoughWallFunction requires 3 entries:

Ks
Cs
value
What does it mean "value"?

For example In the dam break with obstacle tutorial the entries are:
Ks uniform 0.0001;
Cs uniform 0.5;
value uniform 5e-07;
What does it mean value uniform 5e-07?

Also what does
value $internalField
means?

Sorry for the stupid question but I cannot find valid documentation.
Thank you.
Nic86 is offline   Reply With Quote

Old   January 19, 2020, 08:18
Default
  #10
Senior Member
 
Michael Alletto
Join Date: Jun 2018
Location: Bremen
Posts: 341
Rep Power: 6
mAlletto is on a distinguished road
I'm not sure if the value is really required. It is written to the file since the nutwallfunctions are derived from the fidedValue boundary condition.
mAlletto is offline   Reply With Quote

Old   January 20, 2020, 01:08
Default
  #11
New Member
 
Join Date: Nov 2019
Posts: 24
Rep Power: 2
Nic86 is on a distinguished road
Quote:
Originally Posted by mAlletto View Post
I'm not sure if the value is really required. It is written to the file since the nutwallfunctions are derived from the fidedValue boundary condition.
Hi,
I am quite sure that a value is needed because if i delete that line the code does not run and gives me error. It could be that the value is uninfluential when using the nutkwallfunctions but how can i be sure about it? Where can i find official reference about this function??
Thank you
Nic86 is offline   Reply With Quote

Old   January 20, 2020, 04:36
Default
  #12
Senior Member
 
Michael Alletto
Join Date: Jun 2018
Location: Bremen
Posts: 341
Rep Power: 6
mAlletto is on a distinguished road
You find some reference here:



https://www.openfoam.com/documentati...8H_source.html


https://www.openfoam.com/documentati...8C_source.html


some good explanation about wall functions in general (read the chapter standard wall function):



http://www.tfd.chalmers.se/~lada/pos..._report_WF.pdf


wall functions in openfaom


http://www.tfd.chalmers.se/~hani/kur...nfoamFinal.pdf


Unfortunately the nutkroughwallfunction is not described. But the only difference to the nutkwallfunction is the assumed velocity profile in the first cell adjacent to the wall.



Hope this helps


Best


Michael
frantov likes this.
mAlletto is offline   Reply With Quote

Old   January 21, 2020, 23:01
Default
  #13
New Member
 
Join Date: Nov 2019
Posts: 24
Rep Power: 2
Nic86 is on a distinguished road
Excellent! Thank you!
Nic86 is offline   Reply With Quote

Old   October 13, 2020, 05:14
Red face
  #14
New Member
 
Feng
Join Date: Apr 2017
Posts: 2
Rep Power: 0
wind_ is on a distinguished road
Quote:
Originally Posted by Phicau View Post
Hi Jesse,

you need to run the case with a turbulence model and specify nutkRoughWallFunction for nut.

Ks is the equivalent grain roughness (Nikuradse) and Cs is a roughness constant, check the details here: https://cpp.openfoam.org/v3/a01666.html#details

All this is put into play in the damBreakWithObstacle tutorial.

Best,

Pablo
Do it need other Rough wall functions? such as nutURoughWallFunction
wind_ is offline   Reply With Quote

Reply

Tags
dambreak, openfoam, roughness, surface

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[ANSYS Meshing] generation mesh for simulation surface roughness in fluent kamyarmech ANSYS Meshing & Geometry 2 February 29, 2016 13:09
simulation of effect surface roughness on aifoil kamyarmech FLUENT 1 February 28, 2016 09:33
Simulation of surface roughness in fluent sagarmore FLUENT 3 January 12, 2016 14:55
Using Surface Roughness to Approximate Dimple Surface Fang54 Main CFD Forum 1 January 8, 2016 09:40
Cross-compiling OpenFOAM 1.7.0 on Linux for Windows 32 and 64bits with Mingw-w64 wyldckat OpenFOAM Announcements from Other Sources 3 September 8, 2010 06:25


All times are GMT -4. The time now is 17:08.