Q-criterion in Tecplot360

john filippou · November 23, 2021, 14:24

Hello everyone, i want to make clear that i am pretty new to CFD so my question might be idiotic.
I am using tecplot360 in order to make a 3D plot of the wake behind a wind turbine and more precisely i want to model the vorticity.

I have a ".dat" file and i want to load it with the PLOT3D loader in order to calculate the Q-criterion since i read online that this variable is available only in this loader.
So my question is how do i convert the .dat file into a file type that can be loader with the PLOT3D loader.
Thank you in advance.

LuckyTran · November 24, 2021, 00:51

From where does this ".dat" file originate? .dat is not a standardized format and is informally recognized as a text file with data in it.

Can't help you with PLOT3D if you are asking how to use PLOT3D. But Q-criterion can be calculated using tecplot tools.

john filippou · November 24, 2021, 06:25

Quote:

Originally Posted by LuckyTran

From where does this ".dat" file originate? .dat is not a standardized format and is informally recognized as a text file with data in it.

Can't help you with PLOT3D if you are asking how to use PLOT3D. But Q-criterion can be calculated using tecplot tools.

The thing is that q-criterion is only available in tecplot when you load your data with PLOT3D loader.

My .dat file originates from a gfortran code that i am running (lifting line method) and it contains the velocity field in the wake of a wind turbine.

So what i want to do is calculate Q.

What i have achieved so far is to calculate lambda2, which is an alternative to the Q, through a specified set of equations by the use of the second (in magnitude) eigenvalue.

There are two ways to go about using the Q criterion.
1) Manage to load my input file with PLOT3D and use the calculate variables tab (Q-criterion variable)
2) Change the equations set that are used for the lambda2 criterion to make them calculate Q.

Any ideas on how to do one of those two alternatives?
Thank you in advance

LuckyTran · November 24, 2021, 11:59

Or... you know, you could just calculate it. I saw in another thread (rant: why do people always do this!?) that you were looking for the macro to do this...

Here is the download link for Qcriterion.mcr

If you can calculate lambda-2, you can calculate Q-criterion. Actually you calculate something very closely related to Q-criterion along the way to get lambda-2.

john filippou · November 24, 2021, 17:50

Quote:

Originally Posted by LuckyTran

Or... you know, you could just calculate it. I saw in another thread (rant: why do people always do this!?) that you were looking for the macro to do this...

Here is the download link for Qcriterion.mcr

If you can calculate lambda-2, you can calculate Q-criterion. Actually you calculate something very closely related to Q-criterion along the way to get lambda-2.

I found the equations for Q-criterion. By the way the link you sent does not work.

LuckyTran · November 24, 2021, 19:18

Try copying the link into your browser directly. Check pop up blockers. Try another browser. I don't know why the internet doesn't work for you.

LuckyTran · November 24, 2021, 19:20

Code:

#!MC 1400
# Created by Tecplot 360 build 14.0.2.35002

$!ALTERDATA 
  EQUATION = '{Q} = 0'

$!VarSet |NUMVARSINIT| = |NUMVARS|
$!VarSet |NUMVARSINIT| += 1

$!PROMPTFORTEXTSTRING |U|
INSTRUCTIONS = "Enter the variable number for U"
$!PROMPTFORTEXTSTRING |V|
INSTRUCTIONS = "Enter the variable number for V"
$!PROMPTFORTEXTSTRING |W|
INSTRUCTIONS = "Enter the variable number for W"

$!GLOBALTHREEDVECTOR UVAR = |U|
$!GLOBALTHREEDVECTOR VVAR = |V|
$!GLOBALTHREEDVECTOR WVAR = |W|


$!ALTERDATA 
  EQUATION = '{dudx} = ddx(u)'
$!ALTERDATA 
  EQUATION = '{dvdx} = ddx(v)'
$!ALTERDATA 
  EQUATION = '{dwdx} = ddx(w)'
$!ALTERDATA 
  EQUATION = '{dudy} = ddy(u)'
$!ALTERDATA 
  EQUATION = '{dvdy} = ddy(v)'
$!ALTERDATA 
  EQUATION = '{dwdy} = ddy(w)'
$!ALTERDATA 
  EQUATION = '{dudz} = ddz(u)'
$!ALTERDATA 
  EQUATION = '{dvdz} = ddz(v)'
$!ALTERDATA 
  EQUATION = '{dwdz} = ddz(w)'
$!ALTERDATA 
  EQUATION = '{s11} = {dudx}' 
$!ALTERDATA 
  EQUATION = '{s12} = 0.5*({dudy}+{dvdx})' 
$!ALTERDATA 
  EQUATION = '{s13} = 0.5*({dudz}+{dwdx})' 
$!ALTERDATA 
  EQUATION = '{s22} = {dvdy}' 
$!ALTERDATA 
  EQUATION = '{s23} = 0.5*({dvdz}+{dwdy})' 
$!ALTERDATA 
  EQUATION = '{s33} = {dwdz}' 
$!ALTERDATA 
  EQUATION = '{Omga12} = 0.5*({dudy}-{dvdx})' 
$!ALTERDATA 
  EQUATION = '{Omga13} = 0.5*({dudz}-{dwdx})' 
$!ALTERDATA 
  EQUATION = '{Omga23} = 0.5*({dvdz}-{dwdy})' 
$!ALTERDATA 
  EQUATION = '{s2o2_11} = {s11}**2 + {s12}**2 + {s13}**2 - {Omga12}**2 - {Omga13}**2' 
$!ALTERDATA 
  EQUATION = '{s2o2_12} = {s11}*{s12} + {s12}*{s22} + {s13}*{s23} - {Omga13}*{Omga23}' 
$!ALTERDATA 
  EQUATION = '{s2o2_13} = {s11}*{s13} + {s12}*{s23} + {s13}*{s33} - {Omga12}*{Omga23}' 
$!ALTERDATA 
  EQUATION = '{s2o2_22} = {s12}**2 + {s22}**2 + {s23}**2 - {Omga12}**2 - {Omga23}**2' 
$!ALTERDATA 
  EQUATION = '{s2o2_23} = {s12}*{s13} + {s22}*{s23} + {s23}*{s33} - {Omga12}*{Omga13}' 
$!ALTERDATA 
  EQUATION = '{s2o2_33} = {s13}**2 + {s23}**2 + {s33}**2 - {Omga13}**2 - {Omga23}**2'
$!ALTERDATA 
  EQUATION = '{Q} = 2*{Omga12}**2 + 2*{Omga13}**2 + 2*{Omga23}**2 - {S11}**2 - {S22}**2 - {S33}**2 - 2*{S12}**2 - 2*{S13}**2 - 2*{S23}**2'

$!VarSet |NUMVARSFIN| = |NUMVARS|
$!DELETEVARS [|NUMVARSINIT|-|NUMVARS|]

john filippou · November 25, 2021, 05:39

Quote:

Originally Posted by LuckyTran

Code:

#!MC 1400
# Created by Tecplot 360 build 14.0.2.35002

$!ALTERDATA 
  EQUATION = '{Q} = 0'

$!VarSet |NUMVARSINIT| = |NUMVARS|
$!VarSet |NUMVARSINIT| += 1

$!PROMPTFORTEXTSTRING |U|
INSTRUCTIONS = "Enter the variable number for U"
$!PROMPTFORTEXTSTRING |V|
INSTRUCTIONS = "Enter the variable number for V"
$!PROMPTFORTEXTSTRING |W|
INSTRUCTIONS = "Enter the variable number for W"

$!GLOBALTHREEDVECTOR UVAR = |U|
$!GLOBALTHREEDVECTOR VVAR = |V|
$!GLOBALTHREEDVECTOR WVAR = |W|


$!ALTERDATA 
  EQUATION = '{dudx} = ddx(u)'
$!ALTERDATA 
  EQUATION = '{dvdx} = ddx(v)'
$!ALTERDATA 
  EQUATION = '{dwdx} = ddx(w)'
$!ALTERDATA 
  EQUATION = '{dudy} = ddy(u)'
$!ALTERDATA 
  EQUATION = '{dvdy} = ddy(v)'
$!ALTERDATA 
  EQUATION = '{dwdy} = ddy(w)'
$!ALTERDATA 
  EQUATION = '{dudz} = ddz(u)'
$!ALTERDATA 
  EQUATION = '{dvdz} = ddz(v)'
$!ALTERDATA 
  EQUATION = '{dwdz} = ddz(w)'
$!ALTERDATA 
  EQUATION = '{s11} = {dudx}' 
$!ALTERDATA 
  EQUATION = '{s12} = 0.5*({dudy}+{dvdx})' 
$!ALTERDATA 
  EQUATION = '{s13} = 0.5*({dudz}+{dwdx})' 
$!ALTERDATA 
  EQUATION = '{s22} = {dvdy}' 
$!ALTERDATA 
  EQUATION = '{s23} = 0.5*({dvdz}+{dwdy})' 
$!ALTERDATA 
  EQUATION = '{s33} = {dwdz}' 
$!ALTERDATA 
  EQUATION = '{Omga12} = 0.5*({dudy}-{dvdx})' 
$!ALTERDATA 
  EQUATION = '{Omga13} = 0.5*({dudz}-{dwdx})' 
$!ALTERDATA 
  EQUATION = '{Omga23} = 0.5*({dvdz}-{dwdy})' 
$!ALTERDATA 
  EQUATION = '{s2o2_11} = {s11}**2 + {s12}**2 + {s13}**2 - {Omga12}**2 - {Omga13}**2' 
$!ALTERDATA 
  EQUATION = '{s2o2_12} = {s11}*{s12} + {s12}*{s22} + {s13}*{s23} - {Omga13}*{Omga23}' 
$!ALTERDATA 
  EQUATION = '{s2o2_13} = {s11}*{s13} + {s12}*{s23} + {s13}*{s33} - {Omga12}*{Omga23}' 
$!ALTERDATA 
  EQUATION = '{s2o2_22} = {s12}**2 + {s22}**2 + {s23}**2 - {Omga12}**2 - {Omga23}**2' 
$!ALTERDATA 
  EQUATION = '{s2o2_23} = {s12}*{s13} + {s22}*{s23} + {s23}*{s33} - {Omga12}*{Omga13}' 
$!ALTERDATA 
  EQUATION = '{s2o2_33} = {s13}**2 + {s23}**2 + {s33}**2 - {Omga13}**2 - {Omga23}**2'
$!ALTERDATA 
  EQUATION = '{Q} = 2*{Omga12}**2 + 2*{Omga13}**2 + 2*{Omga23}**2 - {S11}**2 - {S22}**2 - {S33}**2 - 2*{S12}**2 - 2*{S13}**2 - 2*{S23}**2'

$!VarSet |NUMVARSFIN| = |NUMVARS|
$!DELETEVARS [|NUMVARSINIT|-|NUMVARS|]

That is really nice of you and thank you but as i mentioned earlier i got the equations for the Q criterion. Comparing my own with yours at the moment. Thank you for your time again.
These are the ones that i have
{Ω}= (0.5*{dudy}-0.5*{dvdx})**2+(0.5*{dudz}-0.5*{dwdx})**2+
(0.5*{dvdx}-0.5*{dudy})**2+(0.5*{dvdz}-0.5*{dwdy})**2+
(0.5*{dwdx}-0.5*{dudz})**2+(0.5*{dwdy}-0.5*{dvdz})**2
{S}={dudx}**2+(0.5*{dvdx}+0.5*{dudy})**2+(0.5*{dwd x} +0.5*{dudz})**2+
(0.5*{dvdx}+0.5*{dudy})**2+{dvdy}**2+(0.5*{dwdy}+0 .5*{dvdz})**2 +
(0.5*{dwdx}+0.5*{dudz})**2+(0.5*{dwdy}+0.5*{dvdz}) **2+{dwdz}**2
{Q}=0.5*({Ω} - {S})

LuckyTran · November 25, 2021, 16:20

I don't understand this tone. They're not my equations. If you have an issue then take it up with tecplot. I don't work for tecplot.

john filippou · November 25, 2021, 17:09

What is weird about my tone? I just said thank you for taking the time to answer and even post the equations. Its all good.

el_mojito · December 10, 2021, 05:40

Quote:

Originally Posted by john filippou

The thing is that q-criterion is only available in tecplot when you load your data with PLOT3D loader.

That's not correct. You can calculate the Q-criterion under "Analyze" -> "Calculate variables" no matter the data format of the file (since Tecplot 2017R2).
Why should the data format matter anyway?

john filippou · December 14, 2021, 07:45

Well Q-criterion does not appear in the list of variables..i solved the issue via the qcriterion equations. Thank you anyway

November 23, 2021, 14:24	Q-criterion in Tecplot360	#1
john filippou New Member ioannis filippou Join Date: Nov 2021 Posts: 8 Rep Power: 5	Hello everyone, i want to make clear that i am pretty new to CFD so my question might be idiotic. I am using tecplot360 in order to make a 3D plot of the wake behind a wind turbine and more precisely i want to model the vorticity. I have a ".dat" file and i want to load it with the PLOT3D loader in order to calculate the Q-criterion since i read online that this variable is available only in this loader. So my question is how do i convert the .dat file into a file type that can be loader with the PLOT3D loader. Thank you in advance.

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November 24, 2021, 00:51		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,754 Rep Power: 66	From where does this ".dat" file originate? .dat is not a standardized format and is informally recognized as a text file with data in it. Can't help you with PLOT3D if you are asking how to use PLOT3D. But Q-criterion can be calculated using tecplot tools.

November 24, 2021, 11:59		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,754 Rep Power: 66	Or... you know, you could just calculate it. I saw in another thread (rant: why do people always do this!?) that you were looking for the macro to do this... Here is the download link for Qcriterion.mcr If you can calculate lambda-2, you can calculate Q-criterion. Actually you calculate something very closely related to Q-criterion along the way to get lambda-2.

November 24, 2021, 19:18		#6
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,754 Rep Power: 66	Try copying the link into your browser directly. Check pop up blockers. Try another browser. I don't know why the internet doesn't work for you.

November 25, 2021, 16:20		#9
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,754 Rep Power: 66	I don't understand this tone. They're not my equations. If you have an issue then take it up with tecplot. I don't work for tecplot.

November 25, 2021, 17:09		#10
john filippou New Member ioannis filippou Join Date: Nov 2021 Posts: 8 Rep Power: 5	What is weird about my tone? I just said thank you for taking the time to answer and even post the equations. Its all good.

December 14, 2021, 07:45		#12
john filippou New Member ioannis filippou Join Date: Nov 2021 Posts: 8 Rep Power: 5	Well Q-criterion does not appear in the list of variables..i solved the issue via the qcriterion equations. Thank you anyway