ICEM output precision
Hi to all
I am using ICEM CFD as a mesher as well as "mesh parser"(importing grids from various formats and then exporting the grid in the format that I want).What I have noticed is that the output (in my case either fluent v6 or CFX) is always single precision.
(By output I mean the node coordinates since connectivity etc is only integers.)
Even if I import a plot3d mesh (in double precision) or a fluent.msh( also double precision from other software) when i export the mesh the output is in single precision.
an example of the first node of the grid
double precision msh file :
-1.9021172349563999e+00 1.0981879031046000e+00 1.9021172349563999e+00
output of icem msh file:
-1.902117235 1.098187903 1.90211723
This causes me problems because in my mesh there are elements which by the single precision transformation produce negative volumes.
I also checked the CFX solver output.It has an option to decide whether single or double precision is needed.I checked double precision but the output was still single.
(I am using ascii files)
I am sure there is a solution to this problem but I can't fint it so any help would be greatly appreciated.
this is a good one for Ansys support.
I would be curious for their reply. I never needed to mesh something that fine.
Yes indeed the resolution seems to be very fine.However we must have in mind that at high reynolds numbers (for example~12-20 million) the boundary layer should be 1d-06 or less which is already close to the single precision margin so smaller values than this could be critical.Also when the aspect ratio of the cells varies very much single precision isn't enough.
Let's say we have a Wind turbine blade which runs at a high reynolds number.
Then we will need a very small boundary layer ~1d-06 but at the farfield we will have cells with size edge 100 or more.In case we had 6 digits in the output(less than single precision) the small cells would be alright but 100,123456 would transform to 100,1234 which could cause problems later on. Imagine if you start with a boundary layer cell and end in a cell of size 100000(ok this is not realistic!!) then all the cell sizes after this margin could cause problems since 100000,1 or 100000,9 would be the same and thus the cells formed from these nodes would have a random orientation.
looked at some .cfx5 mesh files created in icem.
it seems dynamic
grab from file
I asked ansys support and here is the answer:
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