# Moving Mesh Question

Submitted by chewnins on Sat, 06/22/2013 - 07:16

Is there a way to combine a rotary and linear motion so that the axis of rotation moves with the mesh?

When I apply more than one fix move/mesh/gran I do not get the motion I am expecting. I think I need a way to update the rotation point so that after the linear motion the rotation axis origin is updated. Can this be done with a variable that is updated in a for loop with inputs from the linear motion parameters?

Any ideas about how I can set something like this up?

### Forums:

richti83 | Sat, 06/22/2013 - 20:25

### Hi chefnins,

Hi chefnins,

make sure you are using different fix-names for the move-fixes.
Also keep in mind that rotation is non commutative.

Maybe this snipped will help you, it rotates a body arround the point 0 0 1 and aditionaly arround the yaw-(z)-axis:
``` variable omega1 equal 3.1415 variable omega2 equal -3.1415 fix rotcad1 all move/mesh mesh cad1 rotate/variable origin 0. 0. 1. axis 0. 1. 0. omega v_omega1 #rotate arround 0 0 1 fix rotcad2 all move/mesh mesh cad1 rotate/variable origin 0. 0. 0. axis 0. 1. 0. omega v_omega2 #rotate arround COM against rotcad1 fix rotcad3 all move/mesh mesh cad1 rotate/variable origin 0. 0. 0. axis 0. 0. 1. omega v_omega1 #rotate arround COM z-axis```
It should work without /variable, but normely my rotational frequency is not constant (comes from a Multi-Body-System).

Best,
Christian

I'm not an associate of DCS GmbH and not a core developer of LIGGGHTS®
but I have 7 years user experience using LIGGGHTS®, ParaView and LINUX

hansmannb | Thu, 12/12/2013 - 15:36

### Superposition of multiple fix move/mesh

i'm struggleing with the task to creat a common path for my mesh.
what i don't understand ist how the reference frames of the single move/mesh command are bent on eath other.