Error in interpolating data?

Lighto · October 18, 2018, 10:26

Hello everyone,

I am a new Fluent-user and I have a very simple question (I think).

I have defined some custom field functions such as the laminar and turbulent stresses in a k-w-RANS simulation, using viscosity-lam, viscosity-turb, turb-kinetic-energy, density and the gradients. I saved the single components of the stresses (i.e. 12 color-by per time-step) and a combination of them (also defined as a CFF - called "scalar-stress") on some particles injected at the inlet of my domain. To check if "scalar-stress" was correct, I tried to recombine manually (i.e. with matlab) the stresses using the output files but I obtained a different result comparing it to what Fluent has saved as "scalar-stress".

So basically my conclusion is: combining some variables in Fluent is different than doing it in post-processing, but why?
Is this an interpolation issue?

LuckyTran · October 18, 2018, 12:57

How do you calculate gradients in matlab?

Lighto · October 18, 2018, 18:21

I do not calculate gradients in matlab. I save directly $\sigma_{xx},...,\tau_{zx}$ both for laminar and turbulent. Then sum them and do the same calculations I do in Fluent.

October 18, 2018, 10:26	Error in interpolating data?	#1
Lighto New Member Davide Join Date: Jun 2018 Posts: 10 Rep Power: 8	Hello everyone, I am a new Fluent-user and I have a very simple question (I think). I have defined some custom field functions such as the laminar and turbulent stresses in a k-w-RANS simulation, using viscosity-lam, viscosity-turb, turb-kinetic-energy, density and the gradients. I saved the single components of the stresses (i.e. 12 color-by per time-step) and a combination of them (also defined as a CFF - called "scalar-stress") on some particles injected at the inlet of my domain. To check if "scalar-stress" was correct, I tried to recombine manually (i.e. with matlab) the stresses using the output files but I obtained a different result comparing it to what Fluent has saved as "scalar-stress". So basically my conclusion is: combining some variables in Fluent is different than doing it in post-processing, but why? Is this an interpolation issue?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
problem with exporting data to Tecplot	v.jab	OpenFOAM Post-Processing	2	January 11, 2017 08:56
Error when reading data file.	WJXu	FLUENT	7	September 1, 2015 19:34
[OpenFOAM] saving data in paraview	aylalisa	ParaView	3	May 31, 2014 11:38
[General] Warping Cells by Vectors?	ronwelty	ParaView	10	April 29, 2014 05:52
How to update polyPatchbs localPoints	liu	OpenFOAM Running, Solving & CFD	6	December 30, 2005 17:27

October 18, 2018, 12:57		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,797 Rep Power: 66	How do you calculate gradients in matlab?

October 18, 2018, 18:21		#3
Lighto New Member Davide Join Date: Jun 2018 Posts: 10 Rep Power: 8	I do not calculate gradients in matlab. I save directly $\sigma_{xx},...,\tau_{zx}$ both for laminar and turbulent. Then sum them and do the same calculations I do in Fluent.