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

What is the Avearage in dynSmargrinsky model

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 12, 2010, 02:57
Default What is the Avearage in dynSmargrinsky model
  #1
Senior Member
 
wayne.zhang
Join Date: Mar 2009
Location: Shanghai, Shanghai, P.R.China
Posts: 307
Rep Power: 9
waynezw0618 is on a distinguished road
Send a message via MSN to waynezw0618 Send a message via Skype™ to waynezw0618
Dear everyone:

So far as I know, in dynamic smargrinsky model, the original way to calculated cD is unstable , so ensemble average is introduced to resovle the problem such as negetive value of cD. so you can find in http://foam.sourceforge.net/doc/Doxy...agorinsky.html :
cD=<L.M>/<M.M>,
which is intead of

cD=L.M/M.M,

where < > means ensemble average.

But I don`t know what is the " average " in the source code ? it seems like that it is the "Arithmetic average:" for the field

if that the cD is not the funtion of space.as original idea for dynamic model is to make the cD to be the function of time and space--cD=cD(x,t)
so if anyone can tell me where is the code of the original function type for the average here in the code

Thanks

00052
00053 dimensionedScalar dynSmagorinsky::cD(const volSymmTensorField& D) const
00054 {
00055 volSymmTensorField LL = dev(filter_(sqr(U())) - (sqr(filter_(U()))));
00056
00057 volSymmTensorField MM =
00058 sqr(delta())*(filter_(mag(D)*(D)) - 4*mag(filter_(D))*filter_(D));
00059
00060 dimensionedScalar MMMM = average(magSqr(MM));
00061
00062 if (MMMM.value() > VSMALL)
00063 {
00064 return average(LL && MM)/MMMM;
00065 }
00066 else
00067 {
00068 return 0.0;
00069 }
00070 }
00071
waynezw0618 is offline   Reply With Quote

Old   January 24, 2011, 09:54
Default average(volScalarField) -> implementation?
  #2
Member
 
Bernhard Grieser
Join Date: Mar 2010
Location: Zurich, Switzerland
Posts: 30
Rep Power: 7
BernhardGrieser is on a distinguished road
I'd like to know that as well.
How's average(volScalarField) implemented?
BernhardGrieser is offline   Reply With Quote

Old   January 24, 2011, 22:48
Smile Hope this helps!
  #3
Member
 
Charlie
Join Date: Dec 2010
Location: 415 Kinross Dr. Newark, DE 19711
Posts: 78
Rep Power: 6
cheng1988sjtu is on a distinguished road
Hi,

See the source file about average():

http://foam.sourceforge.net/doc/Doxy...8C_source.html

you can see some useful field functions( including average(),pow() etc) there
cheng1988sjtu is offline   Reply With Quote

Old   January 25, 2011, 04:24
Default
  #4
Member
 
Bernhard Grieser
Join Date: Mar 2010
Location: Zurich, Switzerland
Posts: 30
Rep Power: 7
BernhardGrieser is on a distinguished road
Quote:
Originally Posted by cheng1988sjtu View Post
See the source file about average():

http://foam.sourceforge.net/doc/Doxy...8C_source.html

you can see some useful field functions( including average(),pow() etc) there
Thank you very much, Cheng!

Regards,
Bernhard
BernhardGrieser 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
question about turbulence model selection and sensitivity karananand Main CFD Forum 1 February 26, 2010 05:41
Centrifugal Pump and Turbulence Model Michiel CFX 12 January 25, 2010 04:20
Problems bout CFD model of biomass gasification, Downdraft gasifier wanglong FLUENT 2 November 26, 2009 00:27
Reynolds Stress model in CFX vs Fluent Tim CFX 1 October 7, 2009 06:19
Grid resolution for full-scale and down scaled model gravis Main CFD Forum 0 October 2, 2009 10:27


All times are GMT -4. The time now is 17:58.