[rku]

Hi,

The problem I have:

I need to perform cumulative averaging on a vectorField. I don't know if I can use 'counters' as the main time loop is 2 levels above this piece of code. This writes out the surfaceVectorF every timestep!!! surfaceVectorF is initiated in createFields.H. Is there a way for the code to keep it in memory.. I'm not in the main code and this is 2 functions deep so is the only way to do this by putting a variable outside the main time loop?

Or is there a more elegant way to achieve this? I found some threads here and on stackoverflow.. But none that really tackled this specific problem.

Thanks!


Part of my code that I wrote:

vectorField vcField;

//operations done on vcField that fill the values in

if(currTimeIndex%label(meanInterval))
               {
                        Info << " Starting cumulative addition of vcField" <<endl;
                        forAl(surfaceVectorF,i)
                        {
                                surfaceVectorF[i] += vcField[i];
                        }

                        Info << "Writing out surfaceVectorF" << endl;

                        surfaceVectorF.write();

                }
                else
                        if(meanInterval==1)
                        {
                                Info << "meanInterval = 1, no mean calculated" <<endl;

                                forAll(surfaceVectorF,i)
                                {
                                        surfaceVectorF[i] = vcField[i];
                                }
                        }
                        else
                        {
                                Info << "Calculate cumulative value for current timestep" <<endl;
                                forAll(surfaceVectorF,i)
                                {
                                        surfaceVectorF[i] += vcField[i];
                                }
                                // not sure if cumulative addition and averaging can be done in the same loop...
                                Info << "Calculate average value for current timestep" <<endl;
                                forAll(surfaceVectorF,k)
                                {
                                        surfaceVectorF[k] = surfaceVectorF[k]/label(meanInterval);
                                }
                         }

[rku]

Anybody? Please.

[Yann]

Hello,

I don't know in which context you need a cumulative average, but isn't it what the fieldAverage function object does?

https://www.openfoam.com/documentati...ldAverage.html

Regards,
Yann

[rku]

Hello,

The problem is that the fieldAverage is useful for post processing but in my case, after the cumulative average is calculated for the vectorField I want, I still have to perform other operations on it. This is not possible with the fieldAverage function..

Thanks!.

[Yann]

What other operations do you have to perform? If it's doable with functions object, you can use the results of fieldAverage to perform other operations.

Hope this helps,
Yann

[rku]

Hi Yann,

The calculated mean value is used in the code to calculate the bed load flux which in turn is used to calculate the dynamic mesh movement based on exner equation. Can this be done with the post processing tool? If so, could you please let me know where i could find some info on that.?

Thanks!

[Yann]

Hello rku,

If it was for post-processing purpose, you could have tried using fieldAverage then a coded function object to achieve whatever you want to do.

But since you seem to be developing your own solver (am I right?) it's probably better to deal with it right in the solver itself. I'm afraid I cannot help much here, but maybe it's worth having a look at the fieldAverage source code, to check how the averaging is done there and use it as an inspiration for your own solver.

Good luck with that!
Yann

[rku]

Thank you for your time Yann!

Indeed, it is for my own solver.. I'll look into the source code for the fieldaverage function. Just thinking about it, I didn't think this was such a unique problem though that no one has ever tried to average a vectorfield over an interval of timesteps. (or more probably they aren't active on the forum anymore)..

Cheers.

[olesen]

Originally Posted by rku

Thank you for your time Yann!

Indeed, it is for my own solver.. I'll look into the source code for the fieldaverage function. Just thinking about it, I didn't think this was such a unique problem though that no one has ever tried to average a vectorfield over an interval of timesteps. (or more probably they aren't active on the forum anymore)..

Cheers.

This isn't anything particularly unique with the problem, but you either need to have the averaging field stored on the objectRegistry or make it a class member to have it remain persistent in memory.

[abhishekmonu96`]

Hi rku,
Any variable produced in createFields.H is still in the scope of main(). The solver writes that surfaceField so that you can restart the simuation if it get's terminated by some reasopn. Further, you can use the default weighted averaging functions available along with several other field operations for geometricField<> object. I would recomment you to look into the geometric field class source file for same. If you want more specific answer, then you may have to explain more precisely the "cummallative Average" operation.
Have a nice Day and do post a reply!

Thanks and Regards
Abhishek Singh

[rku]

Dear Abhishek Singh,

Thank you for your reply!

The entire problem is that the operations available for the class vectorField (not vol or surface, just the base vectorField) are pretty lackluster.

I tried to solve this problem a bit on my own again and I had a pretty basic question:

Is it possible to interpolate a vectorField to a surfaceVectorField by assigning the geometrical information of each face to the each of the vector in vectorField? Or is it 'just not done' in Openfoam?
Are there any examples of how the variables can be manipulated this way?

Thank you all for your contributions!

[olesen]

Depends on what you mean by "lackluster". If you mean that there aren't any geometric operations for Field or vectorField, you are entirely correct. A Field is simply a List (which is a UList) with intrusive ref-counting (for managing tmps) and various operations such as +=, mag() etc.


Since a vectorField is a really low-level building block, it is used for both representing the internal fields (of a volume, area, point or surface mesh) as well as the parts of the boundary patch fields.


If you need fields with associated geometric information, you should be using one of the GeometricFields (eg, volVectorField, surfaceVectorField etc).


/mark