Floating point exception?

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 February 23, 2000, 07:15 Floating point exception? #1 Ricky Wong Guest   Posts: n/a Hello, I'm trying to model a plain underexpanded jet (still), and I can't get the iterations started. Fluent keeps coming back with floating point exception, (underflow). I don't know what it's complaining about!. I've tried reducing the skewness, checked the grid, re-entered the boundary conditions (trying to start off with a jet at a very low NPR, without turbulence), no joy.. am I grasping at straws or is it something blindingly obvious? please help Thanks

 February 23, 2000, 09:59 Re: Floating point exception? #2 J. McKelliget Guest   Posts: n/a Your model is diverging. The underexpanded jet is almost impossible to converge using Fluent. Make sure you are using the coupled solver, and maybe some kind of initial guess. ashraf88 and anand.jittanakatti like this.

 February 23, 2000, 12:21 Re: Floating point exception? #3 LW Guest   Posts: n/a Can you explain "Underexpanded Jet"? Thanks!

 February 23, 2000, 14:11 Re: Floating point exception? #4 J. McKelliget Guest   Posts: n/a Underexpanded jet = a compressible gas flow where the pressure in the jet is substantially higher than the pressure of the region into which it is discharging - leads to lots of shock and expansion waves etc

 February 23, 2000, 14:27 Re: Floating point exception? #5 John C. Chien Guest   Posts: n/a (1). That's right. (2). Or, (p,ambient/ p,jet exit) < 1. (3). (p,jet exit) is the nozzle exit pressure but still inside the nozzle. (4). Further expansion will occur in the jet, downstream of the nozzle exit, until the pressure at the boundary of the jet matches the ambient pressure. In between, shocks and expansion waves will form in the jet (or plume).

 February 24, 2000, 06:48 Re: Floating point exception? #6 Ricky Wong Guest   Posts: n/a Thanks, Managed to get the model started, stripped it down completely to a laminar, incompressible flow at a very low NPR to begin with and gradually increased the NPR as the solution progressed.

 February 24, 2000, 22:06 Re: Floating point exception? #7 Sung-Eun Kim Guest   Posts: n/a Have you tried to patch a non-zero initial guess for the velocity field ? Please contact your support engineer if the problem doesn't go away.

 February 25, 2000, 11:39 Re: Floating point exception? #8 Ricky Wong Guest   Posts: n/a Thanks for the reply Non-zero intial guesses also prompted the error, It wasn't until I took stripped down the model that it was able to start. Unfortunately I don't think I have a support engineer, I'm a post-grad and the University has an academic license to which I am not the primary licence holder, queries to fluent (europe) support are very slow in replying (if at all) because an academic license is has low priority. Hence I look to the fluent forum for possible help.

 February 7, 2012, 23:31 Floating point error. #9 Member   Join Date: Jan 2012 Posts: 58 Rep Power: 8 Hello. I am getting floating point error:invalid number in my thesis. Ie train moving in tunnel. Can any help me. My email is sheikhnasir39@gmail.com thanks

 February 15, 2014, 23:49 #10 New Member   Chng Join Date: Jul 2012 Posts: 6 Rep Power: 7 One reason could be that the factors are over-relaxed. So if you are confident that BCs, model and solver are appropriate, try reducing the relaxation factor in solution control. jzc, anand.jittanakatti and muis like this.

September 8, 2016, 02:44
#11
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Omid Shekari
Join Date: Jun 2016
Posts: 36
Rep Power: 3
Quote:
 Originally Posted by Ricky Wong ;93808 Thanks, Managed to get the model started, stripped it down completely to a laminar, incompressible flow at a very low NPR to begin with and gradually increased the NPR as the solution progressed.
What does NOR stand for?

September 8, 2016, 02:46
#12
Member

Omid Shekari
Join Date: Jun 2016
Posts: 36
Rep Power: 3
Quote:
 Originally Posted by Ricky Wong ;93808 Thanks, Managed to get the model started, stripped it down completely to a laminar, incompressible flow at a very low NPR to begin with and gradually increased the NPR as the solution progressed.
What does NPR stand for?

June 15, 2017, 02:31
species transport model
#13
New Member

Niaz
Join Date: May 2017
Posts: 11
Rep Power: 2
Quote:
 Originally Posted by Omish What does NPR stand for?
i have the following error in my simulation, kindly if u hav any remedy,post it
# Divergence detected in AMG solver: pressure correction -> Turning off correction scaling!
# Divergence detected in AMG solver: pressure correction -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)

Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Error at host: floating point exception

Error at Node 0: floating point exception

Error at Node 1: floating point exception

Error at Node 2: floating point exception

Error at Node 3: floating point exception

Error at Node 4: floating point exception

Error at Node 5: floating point exception

Error: floating point exception

Error Object: #f

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