fix freeze walls problems

Submitted by Jeff_DONG on Mon, 10/08/2018 - 10:20

Greetings,

I am confused when I use the command: fix freeze.

I'm aiming to build a compression model. I want to build the top cover and bottom plate as the granular wall(the wall is made up of particles by read_data). I use the "fix freeze" command on the wall particles. I fix the movement of the bottom plate, and let the top cover free. Random particles are inserted in the region between two plates.

As the simulation start, the top cover starts to fall down(due to the gravity) and compress the random particles. Ideally, the random particle clusters skeleton should be able to support the falling top cover plate at some point.

The problem is:
It seems that due to the "fix freeze" command, all the force and torque resulted by random particles will be zero out(mentioned in the LIGGGHTS manual, it also says the mass will be infinite compared to other particles). So the top cover will not stop by the random particles skeleton.

Did I use the wrong wat the set up a granular wall, or is there any other way that I can set up the granular walls?
Please find the link to have a look at the simulation record:
https://www.youtube.com/watch?v=uM6JPyX24Ss&feature=youtu.be

Very Appreciate,

Best Regards,
Jeffrey

lumblab227 | Fri, 03/08/2019 - 11:23

Hey, Jeffery.

What you did it not correct if you want to simulate a granular wall instead of a layer.

If you want to model the granular wall, please consider to bond a layer of granules.

Jeff_DONG | Mon, 04/08/2019 - 02:07

Hi,

Thanks. would definitely consider your suggestion.
But I think I've basically solved this problem by using "fix rigid" since I am not considering the deflection of the wall.
Many thanks anyway.

Regards,
Jeff