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-   -   Qdot keeps all zero when using xxxFoam postProcess (https://www.cfd-online.com/Forums/openfoam-post-processing/222155-qdot-keeps-all-zero-when-using-xxxfoam-postprocess.html)

adcpk November 13, 2019 17:13

Qdot keeps all zero when using xxxFoam postProcess
 
I postprocess my resault from reactingFoam openfoam v7



1.
Code:

reactingFoam -postProcess -func Qdot
the fields Qdot appears, but it is all zero


2. If i modify the code by adding a fields named "Qdot" and add code "Qdot=reaction->Qdot()" in main loop, like OF v6

then use
Code:

reactingFoam -postProcess -func "writeObjects(Qdot)"
the fields Qdot appears, but it is all zero


3. but if I do it in run-time data processing using "#includeFunc", everything is good.


How can I get the Qdot if I do not output in runtime.

F_vdp May 14, 2020 09:05

Have you found a solution ?
 
Hi Minguy,

I am trying to post-process results of an engine simulation (between -152CAD and 30CAD hence the starting time being -152) done with the engineFoam under OpenFOAM7.

My goal is also to obtain the heat release rate using the Qdot Functionobjects. However, when I type : "engineFoam -postProcess -func Qdot", here is the error message that I recieve :

Code:

/*---------------------------------------------------------------------------*\
  =========                |
  \\      /  F ield        | OpenFOAM: The Open Source CFD Toolbox
  \\    /  O peration    | Website:  https://openfoam.org
    \\  /    A nd          | Version:  7
    \\/    M anipulation  |
\*---------------------------------------------------------------------------*/
Build  : 7-1ff648926f77
Exec  : engineFoam -postProcess -func Qdot
Date  : May 14 2020
Time  : 10:57:44
Host  : "LAPTOP-6V17VGK6"
PID    : 276
I/O    : uncollated
Case  : /home/francois/OpenFOAM/francois-7/run/combEngineFoam2
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 10)
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create engine time

Selecting engine type crankConRod
Create mesh for time = -152

Selecting engineMesh layered


--> FOAM FATAL ERROR:
Cannot find file "points" in directory "polyMesh" in times "-152" down to constant

    From function virtual Foam::IOobject Foam::fileOperation::findInstance(const Foam::IOobject&, Foam::scalar, const Foam::word&) const
    in file global/fileOperations/fileOperation/fileOperation.C at line 871.

FOAM exiting

The exact same error message is returned when I try your second code line.
It seams that some variables are only available with the solver,meaning that only run-time data processing is possible. However, my simulations are quite time consuming so I would appreciate not to do that.

I am relatively new to OpenFOAM (and in C++ for that matter), have you found a way to use Qdot without doing it during run-time ?

If not, could you quickly explain how to do it in run-time data processing using "#includeFunc" ?

Any help is welcomed,
Thanks in advance,

François VdP.

HPE May 20, 2020 18:20

Hi,

- The error message suggests that you don't have a `points` file which is a part of the mesh definition.
- I have never seen negative time, in your case it seems to be `-152`. Is there any reason? Or is it just some user defined angle (like for engines)?
- Could you please check if `Qdot` is a part of `postProcess` by executing `postProcess -list`? (You don't need to run the FO during the process, but after your simulation, in principle).


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