[naik1991]

Hi,

I am relatively new to openfoam and I have a gearPump Stl file.Till blockMesh it works fine but when I run snappyHexMesh run I am getting an error.Please find the error in the attachment.I am working on windows platform.

Thankyou

[Antimony]

Hi,

I am not sure, and I am taking a guess based on your error message - is your STL file in binary or ascii? If it is in binary, can you convert it to ascii and try again?

Cheers,
Antimony

[naik1991]

Hi ,

I tried in both formats but still getting the same error.

Thanks

[kwardle]

You might try to run surfaceCheck on your STL file.

[aow]

Hi naik,

Your error output is unfamiliar to me, but somehow running snappyHexMesh caused a segmentation fault (sigsegv). As pointed out in the OpenFOAM debugging webpage, this likely is caused by the program trying to access memory outside its allocated space. I've never had this occur with a successfully compiled OpenFOAM installation even when I've used a bad .stl file (open surface geometry, etc...); snappyHexMesh would just fail and generate an output saying some condition was violated and it had to terminate.

First of all, could you post your snappyHexMeshDict script for the case you're attempting to build? There may be a critical error or typo made there.

Secondly, does snappyHexMesh work for the tutorials? If it does, then I suppose it could be your .stl file, in which case you should check it to be sure it doesn't have errors. If the file isn't too detailed, I like to plot it using Matlab (see script below; note that the file must be in ascii format for it to work).

function [vertCoord,normVec] = STLplotter(STLfileName)
tri = [1,2,3];
fID = fopen(STLfileName,'r');
fgets(fID); % skip first line "solid <solidName>"
dataLine = fgets(fID);
splitLine = strsplit(dataLine);
count = 1;
surfCount = 1;
while strcmp(splitLine{1},'endsolid') == 0 % detect end of file
if count == 1 % (for a closed solid) outward-pointing surface normal vector
normVec{surfCount} = [str2double(strsplit(splitLine{4})),str2double(strs plit(splitLine{5})),str2double(strsplit(splitLine{ 6}))];
elseif count == 3 % x,y,z coordinates of first vertice
vertCoord{surfCount}{1}(1) = str2double(strsplit(splitLine{3}));
vertCoord{surfCount}{2}(1) = str2double(strsplit(splitLine{4}));
vertCoord{surfCount}{3}(1) = str2double(strsplit(splitLine{5}));
elseif count == 4 % x,y,z coordinates of second vertice
vertCoord{surfCount}{1}(2) = str2double(strsplit(splitLine{3}));
vertCoord{surfCount}{2}(2) = str2double(strsplit(splitLine{4}));
vertCoord{surfCount}{3}(2) = str2double(strsplit(splitLine{5}));
elseif count == 5 % x,y,z coordinates of third vertice
vertCoord{surfCount}{1}(3) = str2double(strsplit(splitLine{3}));
vertCoord{surfCount}{2}(3) = str2double(strsplit(splitLine{4}));
vertCoord{surfCount}{3}(3) = str2double(strsplit(splitLine{5}));
elseif count == 7
vecBase{surfCount} = [sum(vertCoord{surfCount}{1}),sum(vertCoord{surfCou nt}{2}),sum(vertCoord{surfCount}{3})]/3;
count = 0;
surfCount = surfCount+1;
end
dataLine = fgets(fID);
splitLine = strsplit(dataLine);
count = count+1;
end
surfCount = surfCount-1; % the loop overshoots by 1
fclose(fID);
figure(); hold on
for i = 1:surfCount
trisurf(tri,vertCoord{i}{1},vertCoord{i}{2},vertCo ord{i}{3})
quiver3(vecBase{i}(1),vecBase{i}(2),vecBase{i}(3), normVec{i}(1),normVec{i}(2),normVec{i}(3))
end
hold off

This way you can easily manipulate the surface and see if any faces have incorrect coordinates, have normal vectors pointing in weird directions, etc... If everything looks fine and you're not sure how to load it into ParaView by itself (I've not tried to do such a thing myself), then see if you can successfully load it with enGrid, which is an open-source mesh generation and manipulation software.

Finally, this forum post may have a point. It's suggested there that perhaps running out of disk space may be the issue, or, you may have forgotten to clean up the case before retrying to build it, which can cause failures in building cases.

Best regards,

Andrew

[Antimony]

Hi,

In which case, can you open your ASCII STL file using a text editor and see that there is a word after "solid" in the first line and then there is an "endsolid" at the end of the file?

Cheers,
Antimony

[naik1991]

Hi ,

thank you guys for the reply.The problem is sorted.There was some problem while exporting from the CAD software.Now its working fine.

Regards,
Anirudh

[aow]

If you don't mind my asking, what was the issue? I use CAD software (Autodesk's Inventor, which is free for students) to generate ascii format .stl files a lot and usually don't have issues (I try to keep the precision very high), but would like to know in case something similar pops up.

Glad you could figure out your issue!

[naik1991]

Hi Andrew,

I use Creo.I think the file was corrupted because when i tried opening the ASCII stl file , the file was unreadable in notepad .But again we saved the stl file in ASCII format from Creo and the problem was solved.Even i dont know what exactly the problem was.

Regards

[Tobi]

Hi,

if you are new to FOAM and the meshing procedure, you can check this out. You might find some interesting points: http://holzmann-cfd.de/index.php/en/4-create-a-project

[naik1991]

Hi Tobias,

Thank you,I am working on gear pump and the snappyHexMesh worked fine.But now i want to do snappyHesxMesh for different angular orintations of gears.My question is how do I get differnet angular orientations from the Stl file.I am doing a dynamic mesh so I am creating different base meshes.

Thank you