Getting the coordinates of a local coordinate system

Oculosdegrau · October 16, 2020, 11:00

Hello,

I have a local coordinate system that is managed by a motion. Is there a way to get the position of this system at each step (in relation to laboratory) and plot it/export data/use data in a field function? Thank you

cwl · October 17, 2020, 11:03

The first thing that comes to mind - is to place a Point into origin of moving coordinate system, set that Point to follow the Motion and report its coordinates.

Oculosdegrau · October 19, 2020, 04:56

Hello cwl,

I thought about doing this too, but I couldn't figure out how to report the point position. I thought about using the Position field function, but I guess that is not what is meant for (rather to define a quantity over space). Do you know which field function gives me the coordinates of a point? Sorry for the rookie questions!

fluid23 · October 23, 2020, 09:25

Position is a vector quantity. $$Position[0] is X, $$Position[1] is Y, and I bet you can guess Z. I believe you can specify a user defined coordinate system by $$Position(@CoordinateSystem("user csys"))[0], etc...

Next, create a derived part > point and define it at [0,0,0] in your local coordinate system "user csys" then use that as an input for max or min reports of the position vector quantities [0], [1], [2].

That should do it, but I have not tried it myself. If that works for you, please report back.

Oculosdegrau · October 26, 2020, 04:42

Hi Fluid23, thank you for your reply!

Unfortunately that did not work. I did as you said, but the report cannot generate a real result:

Maximum of Position[Z] on Geometry

Part Value (m) Errors
------ -------------- -------------------------------
Point -1.797693e+308 no data, invalid part
------ -------------- -------------------------------
Total: -1.797693e+308 no data, incomplete computation

In my case I have a circular surface (jounal), so I guess I could simply do the surface average of Position[1], but thats pretty janky...

fluid23 · October 26, 2020, 10:06

Not sure, but this could be a problem with how you've set it up. I think I have seen this happen when the location is outside the computational domain. Some screenshots of the report setup and domain would be helpful.

October 16, 2020, 11:00	Getting the coordinates of a local coordinate system	#1
Oculosdegrau New Member Join Date: Sep 2020 Posts: 5 Rep Power: 5	Hello, I have a local coordinate system that is managed by a motion. Is there a way to get the position of this system at each step (in relation to laboratory) and plot it/export data/use data in a field function? Thank you

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
p_rgh initial residual no change with different settings	manuc	OpenFOAM Running, Solving & CFD	3	June 26, 2018 15:53
Micro Scale Pore, icoFoam	gooya_kabir	OpenFOAM Running, Solving & CFD	2	November 2, 2013 13:58
How to write k and epsilon before the abnormal end	xiuying	OpenFOAM Running, Solving & CFD	8	August 27, 2013 15:33
In which coordinates system is expressed velocity	malaboss	OpenFOAM Post-Processing	2	April 18, 2013 06:00
local coordinate system for porousZone	Nico A.	OpenFOAM Programming & Development	0	November 15, 2011 04:32

October 17, 2020, 11:03		#2
cwl Senior Member Chaotic Water Join Date: Jul 2012 Location: Elgrin Fau Posts: 435 Rep Power: 17	The first thing that comes to mind - is to place a Point into origin of moving coordinate system, set that Point to follow the Motion and report its coordinates.

October 19, 2020, 04:56		#3
Oculosdegrau New Member Join Date: Sep 2020 Posts: 5 Rep Power: 5	Hello cwl, I thought about doing this too, but I couldn't figure out how to report the point position. I thought about using the Position field function, but I guess that is not what is meant for (rather to define a quantity over space). Do you know which field function gives me the coordinates of a point? Sorry for the rookie questions!

October 23, 2020, 09:25		#4
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	Position is a vector quantity. $$Position[0] is X, $$Position[1] is Y, and I bet you can guess Z. I believe you can specify a user defined coordinate system by $$Position(@CoordinateSystem("user csys"))[0], etc... Next, create a derived part > point and define it at [0,0,0] in your local coordinate system "user csys" then use that as an input for max or min reports of the position vector quantities [0], [1], [2]. That should do it, but I have not tried it myself. If that works for you, please report back.

October 26, 2020, 10:06		#6
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	Not sure, but this could be a problem with how you've set it up. I think I have seen this happen when the location is outside the computational domain. Some screenshots of the report setup and domain would be helpful.