CFD Online Discussion Forums - Qdot keeps all zero when using xxxFoam postProcess

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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.

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.

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).

I have the same problem that, if I do post-processing Qdot after computation, the results are all zero when plotted in paraFoam. Any thing we are missing here? Appreciate any help.

Hi all,

Has anyone resolved this problem? I also experienced the same problem in OF 10. I want to post-process by calculating Qdot, however, the results are 0. I use reactingFoam solver with LES and PaSR model.

Thanks :)

I ended up using run-time data processing function. As written in the user guide, you include the Qdot function in functions sub-dictionary in the case controlDict file. (see OpenFOAM User Guide section 6.2.2).

Thank you Charles for your reply.

Well, I had done that too. But, I forgot to include the function object within one of my simulations and wanted to calculate it while post-processing it.

So, I guess I need to re-run my simulation haha :,)