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

fvc::ddt(alphac) equals zero

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 3, 2017, 03:10
Default fvc::ddt(alphac) equals zero
  #1
Senior Member
 
Dongyue Li
Join Date: Jun 2012
Location: Torino, Italy
Posts: 757
Rep Power: 10
sharonyue is on a distinguished road
Hello guys,

Below is the pressure equation In MPPICInterFoam:
Code:
fvScalarMatrix p_rghEqn
        (
            fvm::laplacian(Dp, p_rgh)
         ==
            fvc::ddt(alphac) + fvc::div(alphacf*phiHbyA)
        );

//Info << fvc::ddt(alphac);
The problem is that fvc::ddt(alphac) is zero all the time. After commenting out this term, the solver gives the same result.

Below is from Jasak:
HTML Code:
Thus, if you try to evaluate the ddt the way it is written, it will recognise that the field does not have the oldTime() level stored and will use the current value to initialise it. Basically, fvc::ddt(magSqr(U)) will always give you zero, which is wrong.
One reason is that the alphac is so small, but it should not be zero. I am not sure ifs a bug.
__________________
Im the translator of OpenFOAM User Guide Chinese Edition! But always newbie on CFD.

http://dyfluid.com/en.html
sharonyue 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
Does pressure drop equals the dissipation within the fluid domain Onze Main CFD Forum 0 December 25, 2016 02:38
How to get motionU_ liu OpenFOAM Running, Solving & CFD 18 June 20, 2007 13:34


All times are GMT -4. The time now is 09:49.