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-   -   1.#qnb (http://www.cfd-online.com/Forums/fluent/76997-1-qnb.html)

marye June 10, 2010 05:34

1.#qnb
 
Hello,

when I run my program, it stops at 3 iterations and on Fluent I can read "solution is converged"
and I have 1.#QNBe+00 that appears...

Does anyone know why?

I replace my real by float but it doesn't change the result.

Ethan August 8, 2010 18:38

Hi
 
Hey, I am getting the same problem with 1.#qnb. I was wondering how did u replace your real by float?

Thanks

arslan July 31, 2012 17:32

i had the same problem
 
the problem i solved was a very simple: axissymmetric (horizontal) channel. I set up a axis BC at the upper boundary of my channel and get this error:

iter continuity x-velocity y-velocity time/iter
! 1 solution is converged
1 1.#QNBe+00 1.#QNBe+00 1.#QNBe+00 0:00:12 999

when i change: the upper boundary set a Wall BC, and the bottom set the Axis BC all fixed and a solution was gone..:)
I've heard before that Axis BC must be only horizontal...it seems that this boundary must be also a lower boundary...in my simple geometry at least))))

hope that it will be helpful...to someone..)))

pakk November 15, 2013 13:07

For those who were directed to this forum by google searching for "QNBe":

1.#QNBe+00 is what Fluent shows when it really does not know what to do, for example when somewhere in the calculation there was a 0/0.

In floating point operations, 0/0 results in NAN (Not Any Number). In Fluent, this is #QNAN. Fluent wants to represent this in exponential notation:
1.#QNANe+00
The next thing that happens is that Fluent wants to represent is with 4 digits. N is bigger than 5, so the A is rounded up to B, and it becomes
1.#QNBe+00

If you see this, it means that something in the calculation went wrong. It can have many, many different causes.

flotus1 November 16, 2013 06:52

In this specific case, people really should have read the manual.
It clearly states that the axis of symmetry in an axisymmetric simulation has to coincide with the x-axis.

hem233 November 19, 2013 14:35

Hello,

In my case, #QNB is coming after around 3500 iterations. So how can I know what is going wrong?


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