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Error #002100004, Reynolds number is outside of the range.. 

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June 21, 2020, 05:39 
Error #002100004, Reynolds number is outside of the range..

#1 
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Sumin Park
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Hi everyone.
I'm currently analyzing the dry cask which cooling the spent fuel assembly. The spent fuel assembly is 9000W/m3 heat source. But I have a problem in my case. The "Reynolds number" problem occurred when i analyzed my case through Laminar model in the atmosphere domain(you can see that area in figure 1). So, i changed the turbulence model from Laminar(none) to SST. After analysis, the Reynolds number problem disappeared in the atmosphere domain but it occurred in the gap domain(you can see the gap domain in figure 2). The gap domain is very thin hollow cylinder and the thickness is 6mm. I can't understand why the problem is occurred. The Reynolds number in the gap domain is about 52.128. I think it has small value and even i used the SST turbulence model. summary Laminar model > Reynolds number error occurred in Atmosphere domain, SST model > Reynolds number error occurred in gap domain. Please help me... I can't believe my results because of this error. 

June 21, 2020, 06:45 

#2 
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Glenn Horrocks
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The Reynolds Number "error" really should be a warning only. It is just saying that you should check whether this flow is laminar or not, and if it is turbulent you should use a turbulence model. So rather than just do what it says you should look at this flow and work out whether it is turbulent or not.
Note the Rayliegh number is the nondimensional number of relevance to free convection flows to determine whether it is turbulent or not, not Reynolds Number. (For most free convection cases, anyway). Also I note your residuals are not converging very well. Refer to this FAQ for that issue: https://www.cfdonline.com/Wiki/Ansy...gence_criteria
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June 22, 2020, 11:18 

#3 
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From the convergence diagnostics, I can tell you are running multiple Mass and Momentum/Heat Transfer subsystems
Unless you setup the case using beta features with nonconstant domain physics (and you know what you are doing after that), I am afraid your setup is missing a few domain interfaces definitions. You may be solving a different problem than you expect. Hope I am mistaken
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June 23, 2020, 03:12 

#4  
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Sumin Park
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Quote:
I understand about Rayleigh number that distinguish the Turbulent and Laminar. So, Can i neglect the "warning of Reynolds number?" (because the Turbulent and Laminar is decided by Rayleigh number instead of Reynolds number in the Free convection system.) I have a question in terms of Reynolds number. I actually used the turbulence model(SST) in my case. But the Reynolds number warning occurred in the gap domain. I think that this is due to the laminar flow in the gap domain. is it correct?(actually the Reynolds number in the gap domain is about 50.) 

June 23, 2020, 03:16 

#5  
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Sumin Park
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Quote:
i actually checked the all interfaces but there is no problem.. I read your answer and i understood that the Reynolds number error occurred because of the wrong interfaces, right?? Then,, i will check interfaces again!! 

June 23, 2020, 03:31 

#6 
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Glenn Horrocks
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If you know Rayleigh number is the important parameter to determine whether the flow is laminar or turbulent then you can ignore the message. But you say the Reynolds number in the gap is 50  you should not be using Reynolds numbers if Rayleigh number is the important parameter. You have to be consistent. You should work out the Rayleigh number in the gap and determine if that Rayleigh number is turbulent.
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June 28, 2020, 09:51 

#7  
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Sumin Park
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Quote:
Let me ask you one more question. Are results i got correct regardless of this error(warning)? For example, because the Reynolds number is exceeded in the special point in the gap domain, so the results i got are wrong. So, the warning occurred. 

June 28, 2020, 18:52 

#8 
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Glenn Horrocks
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The warning/error is nothing to do with whether your simulation is accurate. As discussed, Rayleigh number is the important parameter, not Reynolds number.
For the simulation to be accurate you need to consider many more issues than just the Reynolds or Rayleigh numbers. See FAQ: https://www.cfdonline.com/Wiki/Ansy..._inaccurate.3F
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cfx, cfx & fluent, heat transfer 
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