[Crane_]

Hello, everyone.
I meet a trouble while setting pressure gradient. My inlet pressure gradient is time-varying, and there is a formula looks like dp/dy=acos(ωt). ZeroGradient and fixedGradient are all useless for me. How could I write this inlet condition?
I would appreciate it if someone could give me some ideas.

[Pappelau]

Hello Crane,
i don't know if u already found a solution for your problem, if not :


Go to the userguide for foam there u will find this chapter :
https://cfd.direct/openfoam/user-guide/v9-boundaries/
5.2.3.4 Time-varying boundary conditions (Openfoam 8/9)



I think u find your answer there

[Crane_]

Originally Posted by Pappelau

Hello Crane,
i don't know if u already found a solution for your problem, if not :


Go to the userguide for foam there u will find this chapter :
https://cfd.direct/openfoam/user-guide/v9-boundaries/
5.2.3.4 Time-varying boundary conditions (Openfoam 8/9)



I think u find your answer there

Pappelau:
Thank you very much for your kind reply. Actually I know these time-varying boundary conditions, but I think they can only used for pressure condition, instead of pressure gradient condition. For pressure gradient, I only find conditions like zeroGradient and fixedGradient, but they all can't be used for changing gradient.

[Pappelau]

The Function1 should be implemented in FixedGradient also:

find $FOAM_SRC/finiteVolume/fields/fvPatchFields -type f -name "*.H" | xargs grep -l Function1


OpenFOAM-8/src/finiteVolume/fields/fvPatchFields/derived/uniformFixedGradient/uniformFixedGradientFvPatchField.H


at least does the search say so (I never used variable gradients)

[JulioPieri]

Originally Posted by Pappelau

The Function1 should be implemented in FixedGradient also:

find $FOAM_SRC/finiteVolume/fields/fvPatchFields -type f -name "*.H" | xargs grep -l Function1


OpenFOAM-8/src/finiteVolume/fields/fvPatchFields/derived/uniformFixedGradient/uniformFixedGradientFvPatchField.H


at least does the search say so (I never used variable gradients)

I believe this is true. Instead of writing

wall
    {
        type            fixedGradient;
        value           uniform 416.67;
    }

you could replace "uniform" for "table" and write ((1 100)(2 120)), or something like that. Not sure if it will work.

From the UserGuide link provided:

table: inline list of (time value) pairs; interpolates values linearly between times.

In any case, this can be very easily done with swak4Foam

[Crane_]

Thanks for your help. I got some inspiration from both of your replies, and write like this

 
INLET      
    {
        type            uniformFixedGradient;
        uniformGradient   cosine;
                    frequency        0.2;
                    amplitude        2*pi/5.00*1.00;
                    scale            1;  // Scale factor for current
                    level             0;  // Offset
     }

and I found that pressure changes over time and space. I think it may be true but the final results of my case is still different with existing calculation results. Perhaps there are some errors outside the boundary conditions.
Anyway, thanks for giving me ideas to solve the problem.

[Sakun]

Hello everyone,


Sorry to jump into this thread,


I am running compressor blade simulation and i need to give total pressure gradually for my simulation. can get some suggestions from your expertise ?


Thanks in advance