[2015mohammad2015]

hi forum

i want to write expression for moving cylinder in a water, cylinder have a circulation in the box not rotation

finally i found that must write expression for moving mesh

i define the expression but it doesn't work.!!!!!!!

where should i specify the defined expression ???? ( in specified displacement ?)

please help me

<it's force major>

[ghorrocks]

Mesh Velocity X is the mesh velocity from the last time step. It is zero at the start of the simulation. So your expression will always just return zero and no motion will occur.

Try something like this for your displacement expression:
1 [m/s] * t

[hhm747]

Attachment 39811Hi,
I have almost similar problem, but for a rotational movement of an opening inside the fluid domain.

I tried to use moving mesh (dynamic mesh) for simulating, but I don't know how to set the boundary condition for Mesh Motion. In fact, It is not clear how to specify the rotational displacement of mesh.



Indeed, I read Ansys toturial for Ball check valve. In that case, they could use rigid body for specifying mesh motion. but here I know the angular speed of opening, and don't need to do expensive FSI simulation.

I appreciate if you could help me out of this trouble.

hhm747

[singer1812]

angdisp=0.04 [rad/s]*t

Make sure your coordinate system is centered correctly or you will either have to move the system or do a coordinate transfer on the expression.

[hhm747]

Thank you for your useful comment.
I tried to define angle displacement, but CFX says that THETA in Mesh Motion has to be in meter. so I used this expression for solving the problem:

X1, Y1 the coordinate of the new pivot
Raxis= sqrt((x-X1)^2+(y-Y1)^2)
Raxis*Angularspeed* t /1[rad]

but the geometry completely moved.

Then I defined Cartesian components for displacement based on the rotation speed as follows:

MotionX=Raxis*Angularspeed* t*sin(Angle) /1[rad]
MotionY=Raxis*Angularspeed* t*cos(Angle) /1[rad]

It changed the shape of profile instead of rotating it.
I tried some ways but however the profile doesn't rotate .

I appreciate If guide me.

THANKS