Fluent exceeding Solution Limits on faces

bawfuls · July 9, 2012, 20:44

I am using Fluent with a compiled UDF to provide some boundary conditions, specifically a wall heat flux (but the UDF should be irrelevant to this particular issue). I have set the minimum and maximum temperatures in Fluent to 200 K and 2200 K, respectively via the Solution Limits box under Solution Controls. Despite this, when I use the UDF command F_T(face,f_thread) to query the temperature on a boundary face, Fluent often returns a value well outside these temperature limits (including very negative values). Do the Solution Limits specified under Solution Controls not apply to faces? How can I force Fluent to limit ALL temperatures (including faces) to these limits?

flotus1 · July 10, 2012, 00:20

Maybe you could use a bounded scheme (like first order upwind) for the computation of the Energy equation.

bawfuls · July 10, 2012, 15:49

Quote:

Originally Posted by flotus1

Maybe you could use a bounded scheme (like first order upwind) for the computation of the Energy equation.

I am already using first order upwind for the energy equation in this case, so that doesn't seem to be the issue.

flotus1 · July 10, 2012, 16:34

You are right, with a first order upwind scheme, over- and undershoots should not appear, especially when the range of the variable is set as a limit for the solver.

I'd be interested in a solution to this problem too.
My current analysis features a melting process in which the liquidus temperature is exceeded before the cell is fully melted.

July 9, 2012, 20:44	Fluent exceeding Solution Limits on faces	#1
bawfuls New Member Join Date: Jul 2010 Posts: 7 Rep Power: 4	I am using Fluent with a compiled UDF to provide some boundary conditions, specifically a wall heat flux (but the UDF should be irrelevant to this particular issue). I have set the minimum and maximum temperatures in Fluent to 200 K and 2200 K, respectively via the Solution Limits box under Solution Controls. Despite this, when I use the UDF command F_T(face,f_thread) to query the temperature on a boundary face, Fluent often returns a value well outside these temperature limits (including very negative values). Do the Solution Limits specified under Solution Controls not apply to faces? How can I force Fluent to limit ALL temperatures (including faces) to these limits?

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July 10, 2012, 00:20		#2
flotus1 Senior Member Alex S. Join Date: Jun 2012 Location: Germany Posts: 465 Rep Power: 10	Maybe you could use a bounded scheme (like first order upwind) for the computation of the Energy equation.

July 10, 2012, 16:34		#4
flotus1 Senior Member Alex S. Join Date: Jun 2012 Location: Germany Posts: 465 Rep Power: 10	You are right, with a first order upwind scheme, over- and undershoots should not appear, especially when the range of the variable is set as a limit for the solver. I'd be interested in a solution to this problem too. My current analysis features a melting process in which the liquidus temperature is exceeded before the cell is fully melted.