Config file - load as function of coordiantes

[tuanhie...@gmail.com]

Hello,

I would like to know how to write correctly the config file for an issue where the loads are not constant but functions of (x,y,z).

Thanks,

Hiep

[Lukasz Kaczmraczyk]

Hello,

Config reader cannot apply such forces. MoFEM can handle those cases, but not when you set mesh from the config file. If you tell how you like to have it, we can quickly add such capability.

For example, we can restrict to varying linear loads; it should be no problem at all.  Then in config parameter, one should supply coefficients a, b and c, 

f (x,y,z) = a*x+b*y+c

I can ask one of my coworkers to add that for you.

Kind regards,

Lukasz

[tuanhie...@gmail.com]

Hello,

Thanks for your answer. It is exactly that I am looking for at the moment: a load as a linear function of x,y,z. I hope that you can make available this option ASAP.

For a particular case, do you think that I can use a constant moment load in the following case in stead of a force load as linear function of u?

Best regards,

Hiep

[Lukasz Kaczmraczyk]

I can make that available for you next week, if that is ok. I working now on new release, and this will be added there.

[Karol Lewandowski]

What about 'FLUID_PRESSURE_FE' ?

[Lukasz Kaczmraczyk]

Thanks Karol,

Yes, that will do the work, but only if force is normal to the surface. Is a special case for applying forces for fluids. However, I've not added this to config file reader. 

The force and pressure element has a general implementation that any varying force can be applied, only we need to extend config reader to handle those cases.

Lukasz

[Lukasz Kaczmraczyk]

Hello,

It is working now, that functionality is added to the core library users modules,  and further to fracture module.

You will have to pull changes from master branch in core lib and then from fracture user module.

For a couple months we switch to spack as a main installation method. MoFEM is installed with spack on EDF secure server as well. You can see documentation here,  

http://mofem.eng.gla.ac.uk/mofem/html/install_spack.html

To make it short:

git clone --single-branch -b mofem https://github.com/likask/spack.git
. spack/share/spack/setup-env.sh
spack install mofem-fracture-module@0.9.49
spack view symlink -i um_view_v0.9.49 mofem-fracture-module@0.9.49

You can have older version as well:

spack install mofem-fracture-module@0.9.48
spack view symlink -i um_view_v0.9.49 mofem-fracture-module@0.9.48

To add linear pressure to the surface, you do it as follows,

[block_10]
id=100
add=BLOCKSET
name=LINEAR_PRESSURE
# Linear pressure is defined by equation p(x,y,z) = A*x + B*y + C*z + D
user1=0.    # This is A
user2=0.    # This is B
user3=1.    # This is C
user4=-1.   # This is D

You can see that the linear distribution of pressure is assumed. If you need something more sophisticated let me know. You can have on the same surface multiple loads if you like. You mark surface as before, only difference is parameters of the block.

Kind regards,

Lukasz

[tuanhie...@gmail.com]

Thanks Lukasz,

The new version with linear pressure works very well in my case. 

Could you apply a "pressure" (a surface force in fact) that is not perpendicular to a surface (BLOCKSET or SIDESET)?

Best regards,

Hiep

[Lukasz Kaczmraczyk]

If it is constant, you can do it by applying force. If is linear, that is not yet implemented.

[tuanhie...@gmail.com]

Thanks for your answer.

In MoFEM, can the force be applied only on NODESET, or a SIDESET can be used ? 

Regards,

Hiep

[Lukasz Kaczmraczyk]

Hello,

Forces are NODSETS, this is not our convention, but inherited from Cubit, see example

[block_1004]

# Example applying force boundary conditions

id=2004

add=NODESET

force_magnitude=1

moment_magnitude=1

force_fx=1

force_fy=1

force_fz=1

moment_mx=1

moment_my=1

moment_mz=1

L.