SimScale CAE Forum

[solved] Low mean Courant number but Massive Maximum

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#1

Hi there I am running a conjugate heat transfer simulation for a truck with an aircurtain. The point to to see whether aircurtain are effective for holding in cold refrigerated air while the doors are open for unloading.
Do to the nature of this I need an analysis of around 10/20min. Therefore my write time interval is extremely large as to not use too much memory.
I roughly calculated a timestep of 0.003sec for a velcity of 8.5m/s and a cell size of 0.04m.
Somehow the mean courant number is coming back normal at just over 0.7 (not ideal but okay) but a max in the truck body solid (solid 1) of 62541!!
If anyone can help it will be hugely appreciated!
https://www.simscale.com/projects/CalvinVW/aircurtain_truck/

Region: solid_0 Courant Number mean: 0.0017055771424 max: 0.288402683643
Region: solid_1 Courant Number mean: 0.721049487971 max: 62561.1876531

#2

Hi @CalvinVW!

A general option would be to activate the automatic timestep. Let me tag our PowerUsers @Get_Barried, @vgon_alves & @Anware here who might help you out with this one.

Cheers,

Jousef

#3

HI @jousefm
I thanks so much for your reply. I have done this before however this lead to a timestep of something like 8E-14… which is seems linked to the 62561 courant number. Thus sim ran out of memory and showed huge drop in residuals as clearly not much is changing between a timestep that small

#4

Hi @CalvinVW!

Just browsed through the forum and completely missed to get back to you - many apologies!! Can you just let us know what fixed the error so that other users who might find your post can use your solution for their case?

Thanks a ton!

Jousef

#5

Hi @jousefm

I was just extremely silly and was using a conjugate instead of a convective solver!!
Really sorry for that, was a rookie error!

#6

No worries @CalvinVW!

Finding mistakes by yourself is the best case scenario I would say :wink:

Happy SimScaling!

Jousef

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