CFX and Transient Thermal Results

bhavik139 · March 27, 2013, 12:57

I used transient thermal and CFX with same setup but I am getting differences in the results. So can anyone guide me regarding this. Actually I want to use the thermal results in Transient structural to determine thermal stresses.

ghorrocks · March 27, 2013, 16:57

FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

bhavik139 · March 27, 2013, 22:44

No I am not getting errors in the results but the results are not matching.

ghorrocks · March 27, 2013, 22:57

So, you have an inaccuracy between the ANSYS and CFX simulations, right? Then the FAQ I quoted is the place to start.

jthiakz · March 28, 2013, 02:47

# provide the CFX case setup / result details clearly
# how much the deviation is, which parameter is deviating

bhavik139 · March 28, 2013, 23:31

I have attached the CFX setup, I am getting the value of max temp different in both cases.
3.jpg

Capture 2.jpg

Capture.jpg

s.jpg

evcelica · March 29, 2013, 14:04

Is everything the same on both simulations, initial conditions, material properties, geometry, etc?
Have you reached a grid independant, and time step independant solution with both simulations. How did you pick your timesteps? Are you converging each timestep in CFX, and if so to what residual level?

Are you sure you put in the same boundary conditions in mechanical, the timesteps can be a bit tricky sometimes, especially when entering a function for multiple time steps.

March 27, 2013, 12:57	CFX and Transient Thermal Results	#1
bhavik139 New Member Bhavik Join Date: Apr 2012 Location: Arlington, TX Posts: 14 Rep Power: 14	I used transient thermal and CFX with same setup but I am getting differences in the results. So can anyone guide me regarding this. Actually I want to use the thermal results in Transient structural to determine thermal stresses.

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March 27, 2013, 16:57		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

March 27, 2013, 22:44		#3
bhavik139 New Member Bhavik Join Date: Apr 2012 Location: Arlington, TX Posts: 14 Rep Power: 14	No I am not getting errors in the results but the results are not matching.

March 27, 2013, 22:57		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	So, you have an inaccuracy between the ANSYS and CFX simulations, right? Then the FAQ I quoted is the place to start.

March 28, 2013, 02:47		#5
jthiakz Member Thiagu Join Date: Oct 2012 Location: India Posts: 60 Rep Power: 13	# provide the CFX case setup / result details clearly # how much the deviation is, which parameter is deviating

March 28, 2013, 23:31		#6
bhavik139 New Member Bhavik Join Date: Apr 2012 Location: Arlington, TX Posts: 14 Rep Power: 14	I have attached the CFX setup, I am getting the value of max temp different in both cases. 3.jpg Capture 2.jpg Capture.jpg s.jpg

March 29, 2013, 14:04		#7
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,167 Rep Power: 23	Is everything the same on both simulations, initial conditions, material properties, geometry, etc? Have you reached a grid independant, and time step independant solution with both simulations. How did you pick your timesteps? Are you converging each timestep in CFX, and if so to what residual level? Are you sure you put in the same boundary conditions in mechanical, the timesteps can be a bit tricky sometimes, especially when entering a function for multiple time steps.