hydraulic gradient with PFV-DEM

Hi,

Did you try using attributes such as FlowEngine.bndCondValue [*] ?
You may also check the example script [**] (mentioned in the above mentioned FlowEngine doc)

[*] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.FlowEngine.bndCondValue
[**] https://github.com/yade/trunk/blob/master/examples/FluidCouplingPFV/oedometer.py

Hi Jérôme,
thank for your reply.
I imposed pressure in [**] as:
flow.bndCondIsPressure=[0,0,1,1,0,0]
flow.bndCondValue=[0,0,a,0,0,0]
for having gradient equal to: i=a/(c*waterUnitWeight) where c is the length in the direction of flow.
and ran simulation for thousands of iterations but i can't see the movement of particles!
Am I doing something wrong??
Azim

Your commands seem correct to me but I'm not really familiar with FlowEngine..

Anyway, on a general note, it is rare there is much too see in YADE qt.View() and I would rely on other indicators to check for a correct simulation definition.

Why not look instead at the plots defined in [**] ?

Hi, the question in unclear.
I would say it is already answered by the example script pointed out by Jerôme [**], where hydraulic gradient is imposed.
Bruno

Hi Jérôme,
I already looked at [**]. they prove the good performance of DEM+PFV.(Thanks to Bruno and Emanuele for this powerful engine).
but my question is about the movement of particles. what is the easiest way to check it??

Hi Bruno,
thanks for your answering my question.
I will be more grateful if you answer my following questions.
1) is my expression (in #2) right for imposed gradient??
2) should we impose macroscopic hydraulic gradient? or Do we need to do something_ like calibration_ as we do for soil particles properties?? because my particle do not move even with many large gradients.
3) how can we watch flow in PARAVIEW??( if my question is irrelevant please tell me to open a new thread.)

To compliment 2) by Robert: if permeability factor is set negative it will
be used as (approximate) Darcy permeability. Otherwise permeability is
predicted based on micrstructure and fluid viscosity, then multiplied by
permeability factor in case it is not 1.
B

Le jeu. 9 août. 2018 17:17, Robert Caulk <
<email address hidden>> a écrit :

> Question #671365 on Yade changed:
> https://answers.launchpad.net/yade/+question/671365
>
> Status: Open => Answered
>
> Robert Caulk proposed the following answer:
> Hello Azim,
>
> 1) Yes, you are imposing a gradient in the Y direction with your
> commands.
>
> 2) Flow engine boundary condition assignments are designed to impose
> "macroscopic hydraulic gradients" on cubical specimens. If you want to
> use this hydraulic gradient to calibrate the macroscopic permeability of
> your sample, you will want to adjust the permeability factor [1] and
> estimate the corresponding macroscopic permeability.
>
> 3) In an attempt to keep this relevant to this thread - if you want to
> see the hydraulic gradient in paraview, you will want to export
> pressures with flow.saveVTK [2].
>
> Cheers,
>
> Robert
>
> [1]
> https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.FlowEngineT.permeabilityFactor
> [2]
> https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.FlowEngineT.saveVtk
>
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Hi Robert,
I really appreciate your help.
>> you will want to export pressures with flow.saveVTK [2].
I want to watch flow with grains together. VTK shows a solid with pressures, it is a very good engine, but not my need.
Thanks again
Azim

Hi Bruno,
I think permeability set to 1 (Default) is my choice.
thanks for your helpful comments.
Azim

Thanks Robert Caulk, that solved my question.