how to plot relative velocity on a plane in POST CFX

rystokes · July 2, 2009, 22:18

Hi,

In my case, a water filled cylindrical domain and its surrounding surface was setup as wall, which rotates at a certain speed, my question is how I can plot the velocity profile(radial, tangential, axial component) relative to the wall in the chart viewer. Can anyone help me with it please?thanks.

Harry

ghorrocks · July 3, 2009, 07:32

Hi,

I assume you did not use a rotating frame of reference - if you did you will have variables in both the stationary and rotating frame of reference in the output file by default.

If it is a stationary frame of reference simulation you will have to generate the rotating frame of reference by generating a vector field (in the variables tab) which is the velocity in the stationary frame of reference plus the component to convert it to the rotating frame. This should be simply r x omega (where "x" means the vector cross product)

Glenn Horrocks

rystokes · July 4, 2009, 04:48

HI, Glenn,

Thanks for your reply. Could you please tell me how to specify a rotating frame of reference in Pre-CFX? I tried to find it in tutorial, but it didn't help me a lot.Thanks in advance.

rystokes · July 4, 2009, 08:20

Hi Glenn,

Do you use domain motion in the basic setting tab of domain details in PRE CFX to specify rotating frame of reference(RFR)? I tried it, but I didn't find the variables of velocity in both stationary and rotating frame of reference in the variable tab in POST CFX.

Could you please help me with it? Thanks.

ghorrocks · July 5, 2009, 07:39

Hi,

Do the rotor/stator example in the tutorials. It uses a RFR.

Also note RFR is a license option which is not included in the basic CFX package. If you can't see it then you might not have that license option.

Glenn Horrocks

rystokes · July 5, 2009, 12:21

Hi Glenn,

Thanks, I got it. By the way, do you know how to express vector cross product in CFX? Thanks.

Harry

ghorrocks · July 5, 2009, 20:26

In what context? The CEL has a cross product function (I think) or you can write it out in full as a CEL expression. Is this what you mean?

Glenn Horrocks

rystokes · July 6, 2009, 01:45

Hi Glenn,

Yes, that's it. But I didn't find vector cross product function in CEL, maybe it doesn't support vector arithmetic. I gotta to write it out. I'm trying to generate the rotating frame of reference by generating a vector field using my current simulations with stationary frame of reference. And this requires to use cross product. Do I need fortran to write it, any good suggestions? thanks.

ghorrocks · July 6, 2009, 02:24

Hi,

CEL does not support vector variables, so make 3 CEL variables representing each component of the vector variable and then write out the cross product in terms of the components. A little messy but still pretty easy.

Glenn Horrocks

July 2, 2009, 22:18	how to plot relative velocity on a plane in POST CFX	#1
rystokes New Member harry Join Date: May 2009 Posts: 29 Rep Power: 17	Hi, In my case, a water filled cylindrical domain and its surrounding surface was setup as wall, which rotates at a certain speed, my question is how I can plot the velocity profile(radial, tangential, axial component) relative to the wall in the chart viewer. Can anyone help me with it please?thanks. Harry

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July 3, 2009, 07:32		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Hi, I assume you did not use a rotating frame of reference - if you did you will have variables in both the stationary and rotating frame of reference in the output file by default. If it is a stationary frame of reference simulation you will have to generate the rotating frame of reference by generating a vector field (in the variables tab) which is the velocity in the stationary frame of reference plus the component to convert it to the rotating frame. This should be simply r x omega (where "x" means the vector cross product) Glenn Horrocks

July 4, 2009, 04:48		#3
rystokes New Member harry Join Date: May 2009 Posts: 29 Rep Power: 17	HI, Glenn, Thanks for your reply. Could you please tell me how to specify a rotating frame of reference in Pre-CFX? I tried to find it in tutorial, but it didn't help me a lot.Thanks in advance.

July 4, 2009, 08:20		#4
rystokes New Member harry Join Date: May 2009 Posts: 29 Rep Power: 17	Hi Glenn, Do you use domain motion in the basic setting tab of domain details in PRE CFX to specify rotating frame of reference(RFR)? I tried it, but I didn't find the variables of velocity in both stationary and rotating frame of reference in the variable tab in POST CFX. Could you please help me with it? Thanks.

July 5, 2009, 07:39		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Hi, Do the rotor/stator example in the tutorials. It uses a RFR. Also note RFR is a license option which is not included in the basic CFX package. If you can't see it then you might not have that license option. Glenn Horrocks

July 5, 2009, 12:21		#6
rystokes New Member harry Join Date: May 2009 Posts: 29 Rep Power: 17	Hi Glenn, Thanks, I got it. By the way, do you know how to express vector cross product in CFX? Thanks. Harry

July 5, 2009, 20:26		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	In what context? The CEL has a cross product function (I think) or you can write it out in full as a CEL expression. Is this what you mean? Glenn Horrocks

July 6, 2009, 01:45		#8
rystokes New Member harry Join Date: May 2009 Posts: 29 Rep Power: 17	Hi Glenn, Yes, that's it. But I didn't find vector cross product function in CEL, maybe it doesn't support vector arithmetic. I gotta to write it out. I'm trying to generate the rotating frame of reference by generating a vector field using my current simulations with stationary frame of reference. And this requires to use cross product. Do I need fortran to write it, any good suggestions? thanks.

July 6, 2009, 02:24		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Hi, CEL does not support vector variables, so make 3 CEL variables representing each component of the vector variable and then write out the cross product in terms of the components. A little messy but still pretty easy. Glenn Horrocks