Autodesk Simulation Mechanical and Multiphysics
The following tips can be helpful for finding and fixing watertightness issues. While this won't fix every problem, it can get you out of some situations. Your mileage may vary.
--- Finding the problem ---
Odds are if you have a "watertightness" problem, the solid mesher has helpfully put the surface mesh lines it deems problematic on layer 2 and 3. So coloring the mesh by layer and the layer control are your friends.
Coloring the mesh by layer number can be activated at any time via the menu "View|Color by|Layer". The layer control is accessible by the menu "View|Options|Layer Control..." and will automatically switch to color-by-layer mode when the Layer Control window is displayed.
You may also want to change drawing modes to eliminate shading -- "View|Display|Mesh" menu -- to make the problem area easier to spot.
Layer 2 lines are red, and layer 3 lines are yellow. If you have a lot of mesh lines, you probably will not see these problem lines right away -- they'll probably be drowned out by green layer 1 lines and orange layer 14 lines. So show the Layer Control, and then in its "Show" column uncheck all layers except 2 and 3. At this point, you probably should be able to see the mesh lines that were deemed problems.
--- Trying to fix the problem ---
The usual fixable cause of trouble when this happens is that the mesh is a bit too coarse for the solid mesher to deal with. So what you need to do is refine the surface mesh in this area. One could do this simply by moving the mesh size slider to the right and remeshing. That's certainly easiest to do. But that can generate a mesh thats finer than it needs to be. So I personally prefer to do more work and just get the mesh in the problem area(s) refined. Here's how I go about it.
First, I change over to line selection mode using "Selection|Select|Lines". Then I click on problem layer 2 or layer 3 line to select it, then right-click it and on the context menu and select "Inquire". I make a note of its length and then do so for a few other layer 2 and layer 3 lines in the problem area(s).
What I do next is gauge the average mesh size in that area. I also sometimes take a look at the CAD model itself -- are these unusually long mesh lines around a small detail? I take this into account when choosing what I think a good alternative mesh size for the problem area would be. For instance, if there's just a few problem lines, I might decide I want to try a mesh size 1/2 or 1/3 their length. If I have some small CAD details and I can guestimate their size, I might decide to try a mesh size 1/2 the width of the detail.
Now I have to tell the mesher about me wanting that mesh size. To do this, I use one or more refinement points, particularly if the problem area is rather small. Change to vertex selection mode using "Selection|Select|Vertices". I then click on a mesh line endpoint somewhere near the middle of a problem area, then right-click it and select "Add|Refinement Points..." from the context menu.
(This dialog will helpfully indicate the estimated mesh size on the parts involved with that mesh vertex; sometimes I take that into account when deciding a mesh size.)
I enter the mesh size I want into the "Mesh size" field. For the "Effective radius", I usually gauge the overall size of the problem area of layer 2/3 lines (I already know the "average" line length for this area from previous inspection) and then enter a value double that, sometimes a little bit more. I press OK and I'm done. For rather oblong problem areas, I might string together a few refinement points with appropriately adjusted effective radii.
Repeat if there are multiple problem areas with layer 2/3 lines.
I then re-mesh the model to see if this fixes the problem.
HTH
Joel Schultz
Software Engineer
Engineering Design and Simulation
Manufacturing Industry Group
Joel Schultz
Principal Engineer
DLS- Simulation
--- Finding the problem ---
Odds are if you have a "watertightness" problem, the solid mesher has helpfully put the surface mesh lines it deems problematic on layer 2 and 3. So coloring the mesh by layer and the layer control are your friends.
Coloring the mesh by layer number can be activated at any time via the menu "View|Color by|Layer". The layer control is accessible by the menu "View|Options|Layer Control..." and will automatically switch to color-by-layer mode when the Layer Control window is displayed.
You may also want to change drawing modes to eliminate shading -- "View|Display|Mesh" menu -- to make the problem area easier to spot.
Layer 2 lines are red, and layer 3 lines are yellow. If you have a lot of mesh lines, you probably will not see these problem lines right away -- they'll probably be drowned out by green layer 1 lines and orange layer 14 lines. So show the Layer Control, and then in its "Show" column uncheck all layers except 2 and 3. At this point, you probably should be able to see the mesh lines that were deemed problems.
--- Trying to fix the problem ---
The usual fixable cause of trouble when this happens is that the mesh is a bit too coarse for the solid mesher to deal with. So what you need to do is refine the surface mesh in this area. One could do this simply by moving the mesh size slider to the right and remeshing. That's certainly easiest to do. But that can generate a mesh thats finer than it needs to be. So I personally prefer to do more work and just get the mesh in the problem area(s) refined. Here's how I go about it.
First, I change over to line selection mode using "Selection|Select|Lines". Then I click on problem layer 2 or layer 3 line to select it, then right-click it and on the context menu and select "Inquire". I make a note of its length and then do so for a few other layer 2 and layer 3 lines in the problem area(s).
What I do next is gauge the average mesh size in that area. I also sometimes take a look at the CAD model itself -- are these unusually long mesh lines around a small detail? I take this into account when choosing what I think a good alternative mesh size for the problem area would be. For instance, if there's just a few problem lines, I might decide I want to try a mesh size 1/2 or 1/3 their length. If I have some small CAD details and I can guestimate their size, I might decide to try a mesh size 1/2 the width of the detail.
Now I have to tell the mesher about me wanting that mesh size. To do this, I use one or more refinement points, particularly if the problem area is rather small. Change to vertex selection mode using "Selection|Select|Vertices". I then click on a mesh line endpoint somewhere near the middle of a problem area, then right-click it and select "Add|Refinement Points..." from the context menu.
(This dialog will helpfully indicate the estimated mesh size on the parts involved with that mesh vertex; sometimes I take that into account when deciding a mesh size.)
I enter the mesh size I want into the "Mesh size" field. For the "Effective radius", I usually gauge the overall size of the problem area of layer 2/3 lines (I already know the "average" line length for this area from previous inspection) and then enter a value double that, sometimes a little bit more. I press OK and I'm done. For rather oblong problem areas, I might string together a few refinement points with appropriately adjusted effective radii.
Repeat if there are multiple problem areas with layer 2/3 lines.
I then re-mesh the model to see if this fixes the problem.
HTH
Joel Schultz
Software Engineer
Engineering Design and Simulation
Manufacturing Industry Group
Joel Schultz
Principal Engineer
DLS- Simulation
