what does post color mode variable x, y, z means?

IronLyon · March 12, 2019, 08:47

I'd like to know in the post, when I choose one of the object or the interface or just the surface, in the color variable options, there are 'x, y, z' which you can choose. So what does it means?
Unbenannt.PNG

2.jpg

Is that means the displacement or something similar? Because the unit is [m]. And for me, I'd like to get the monitor which can show the displacement (I only know the expression like 'force_x()@location' can record the force, but for the displacement expression no idea).

Even the official guide didn't show the details, someone can help? Thank you!

AtoHM · March 12, 2019, 11:01

These are just the coordinates in the model.
You can use them for various things like showing the height of a free-surface isosurface (like here https://cfd.ninja/free-surface-3d/ just with the height coordinate instead of velocity) or positioning of user surfaces for other postprocessing reasons.
What kind of displacement are you looking for? Because usually if not set up otherwise, you won't have something like displacement in a CFD model except if you use mesh displacement in Pre or do FSI.

IronLyon · March 12, 2019, 11:26

Quote:

Originally Posted by AtoHM

These are just the coordinates in the model.
You can use them for various things like showing the height of a free-surface isosurface (like here https://cfd.ninja/free-surface-3d/ just with the height coordinate instead of velocity) or positioning of user surfaces for other postprocessing reasons.
What kind of displacement are you looking for? Because usually if not set up otherwise, you won't have something like displacement in a CFD model except if you use mesh displacement in Pre or do FSI.

Thank you. In my case there is a chamber with only one inlet without the outlet for the gas, the gas blows into the chamber from the hole on the bottom. And there is a liquid metal ball (no gravity but well positioned by the electricalmagnetic field) in the middle of the chamber. When the gas blows from the bottom towards the ball, the ball will move a little bit.

We don't consider the electricalmagnetic field now, I have set the expression such like force_y@'interface of bottom ball' (this interface is on the interface but the gas domain, because the force shows always 0 on the interface of the liquid metal domain). Is this force which I got right to show the force on the bottom of the ball, which produced because of the gas blowing.

I just want to kown the max shift or displacement of the ball. So I need to know the force at first step. (simulation plus the the electricalmagnetic field too complicated)

AtoHM · March 13, 2019, 03:22

Oh wow, you seem to be looking for a lot here. Honestly, this is a very challenging simulation to do and I would conduct a good literature study on how to do something like this.

If the ball is already "solid" (not so hot that it would conduct like a fluid), then you might be able to cut it out of the domain and do an FSI simulation (fluid structure interaction) - you will find tutorials for this on the internet. Another option would be to do a normal simulation of this, extract the force as you did and analytically evaluate the displacement. However if you dont model the electromagnetic field forces and neglect gravity, the ball will just be "blown" away by the gas jet.

If the ball is more like a fluid, it will not only be displaced but also heavily deformed and then I have no idea how to model that.

March 12, 2019, 08:47	what does post color mode variable x, y, z means?	#1
IronLyon Member Join Date: Feb 2019 Posts: 30 Rep Power: 7	I'd like to know in the post, when I choose one of the object or the interface or just the surface, in the color variable options, there are 'x, y, z' which you can choose. So what does it means? Unbenannt.PNG 2.jpg Is that means the displacement or something similar? Because the unit is [m]. And for me, I'd like to get the monitor which can show the displacement (I only know the expression like 'force_x()@location' can record the force, but for the displacement expression no idea). Even the official guide didn't show the details, someone can help? Thank you!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
CFD -post particle variable	sjtusyc	CFX	0	September 14, 2012 23:09
New Variable in CFX Post	Ben	CFX	9	June 20, 2012 19:10
Assign new variable in CFX Post	Ben	CFX	1	August 25, 2008 15:59
Variable for Number of Mesh Elements CFX Post	Matt	CFX	0	August 14, 2008 18:05
Post Processing in FEM	Abhijit Tilak	Main CFD Forum	0	April 26, 2004 12:59

March 12, 2019, 11:01		#2
AtoHM Senior Member M Join Date: Dec 2017 Posts: 703 Rep Power: 13	These are just the coordinates in the model. You can use them for various things like showing the height of a free-surface isosurface (like here https://cfd.ninja/free-surface-3d/ just with the height coordinate instead of velocity) or positioning of user surfaces for other postprocessing reasons. What kind of displacement are you looking for? Because usually if not set up otherwise, you won't have something like displacement in a CFD model except if you use mesh displacement in Pre or do FSI.

March 13, 2019, 03:22		#4
AtoHM Senior Member M Join Date: Dec 2017 Posts: 703 Rep Power: 13	Oh wow, you seem to be looking for a lot here. Honestly, this is a very challenging simulation to do and I would conduct a good literature study on how to do something like this. If the ball is already "solid" (not so hot that it would conduct like a fluid), then you might be able to cut it out of the domain and do an FSI simulation (fluid structure interaction) - you will find tutorials for this on the internet. Another option would be to do a normal simulation of this, extract the force as you did and analytically evaluate the displacement. However if you dont model the electromagnetic field forces and neglect gravity, the ball will just be "blown" away by the gas jet. If the ball is more like a fluid, it will not only be displaced but also heavily deformed and then I have no idea how to model that.