# maximum cell aspect ratio in prism layer

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 November 23, 2021, 11:48 maximum cell aspect ratio in prism layer #1 Member   Pietro Join Date: Jun 2021 Location: London Posts: 40 Rep Power: 3 Hi, Anybody knows a good rule of thumb for maximum aspect ratio allowed in the cells which are in the first prism layer? (I am computing the Aspect ratio as the ratio between the 'Target surface size' and the height of the first prism layer) Exceeding a certain value should lead to problems in accuracy and convergence, if I remember well. But what is such value? Best Pietro

November 23, 2021, 20:13
#2
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Peresvet
Join Date: Mar 2021
Location: USSR
Posts: 32
Rep Power: 3
Quote:
 Originally Posted by pi120 Hi, Anybody knows a good rule of thumb for maximum aspect ratio allowed in the cells which are in the first prism layer? (I am computing the Aspect ratio as the ratio between the 'Target surface size' and the height of the first prism layer) Exceeding a certain value should lead to problems in accuracy and convergence, if I remember well. But what is such value? Best Pietro
The value is that your life won't be long enough to find it. As for the CFD: I have been looking for 5 years with the help of 600 cores and cannot find the point of using it at all.

November 24, 2021, 03:16
#3
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Ashok Chaudhari
Join Date: Aug 2016
Location: Pune, India
Posts: 260
Rep Power: 9
Quote:
 Originally Posted by pi120 Hi, Anybody knows a good rule of thumb for maximum aspect ratio allowed in the cells which are in the first prism layer? (I am computing the Aspect ratio as the ratio between the 'Target surface size' and the height of the first prism layer) Exceeding a certain value should lead to problems in accuracy and convergence, if I remember well. But what is such value? Best Pietro
Yes. It depends. What is the complexity of physics, where in the domain etc. Ideal number is 1:1. But there is no specific number to distinguish the accuracy levels. It's the gut feeling. These studies should be done at starting. For some cases we would be putting 20-30 prism layers in 1mm. Then obviously you wont be able to maintain even 1:5. And nowadays softwares are quite robust. You may be good enough solution for bad meshes. Hope this helps.

 Tags aspect ratio, mesh 3d, prism layer