Simulation Mesh OptimizationPosted byKeith Vittitoeon September
27, 2013 at 7:59 AMOnce the model is simplified to accommodate the
best balance between mesh density and result accuracy, the next
step is to optimize the mesh. Recall from 1-minute calculus that we
need to use something we know to approximate something we dont.
Thinking along those lines, the more regular our tetrahedrons or
triangles are, the more accurate the result will be. It's easy to
calculate the area of right triangles and isoceles triangles.
"Regulah" as they say in the general vacinity of SolidWorks' HQ is
translated as mesh quality or "aspect ratio". Aspect ratio is
calculated three ways by SolidWorks - edge length, normals length,
and inscribed/circumscribed circles check. For higher order
calculations, there is yet another mesh quality check - Jacobian,
but we're not going there.
inscribed/circumscribed circles check(can you tell which one is
better?)Of course, measuring the aspect ratio of millions of
elements is a detailed process. Since we can't affect that
calculation, know that basically SolidWorks is making sure that
most of the mesh elements can be used in the calculation. Let's
pause for a moment to discuss "higher order" as I mentioned above
regarding a Jacobian quality check. By higher order, we are
referencing the exponents of the equation describing the curve we
need to create a mesh element that approximates the shape of the
model face (only 1 comma in that whole sentence). An equation
representing a straight line has no exponent (mx + b = y). As soon
as you step to x^2, the "line" curves. A "higher exponent" like x^3
or x^4 is synonymous with "higher order". I don't want to get
side-tracked with this, so I'll keep it simple - we've been
discussing triangles and tetrahedrons, but we could use mesh
elements that are parabolic to approximate curved surfaces - higher
order elements. Now back to our mesh quality discussion.So, why
does SolidWorks calculate mesh error for us? I'll start by
explaining what makes a "good" mesh. Let's look at the thickness of
a part, as an example. We want our elements size to match that
thickness - exactly one "triangle" high.
Or consider an inside or concave radius. That curve requires a
curved element. If we are using a relatively large element, then
the elements will have to curve, so we either need a higher order
element or better yet, a smaller element so the discretization
error is minimal. Otherwise, we get this "jagged" result around the
radius:
If we dont pay attention to these mesh considerations,
Simulation will do its best to calculate what we ask, but the
result may be elements in the mesh with aspect ratios that
negatively affect our results. Remember, the more simple the shape,
the more regular the shape, the more accuate the result becomes
(perfect vacuum and frictionless ice). Said another way, the
approach to calculating the volume of these two pyramidal shapes is
fairly similar, but one result is going to be much more
accurate...
To avoid providing obviously wrong results, SolidWorks performs
a mesh error check. We can help ourselves, though. To address the
need to minimize the mesh density, and optimize the element aspect
ratio, we can use mesh refinement techniques, the basis of which
I've been attempting to explain. Here's what SolidWorks offers in
order of refinement: Coarse to Fine adjustment of global mesh Mesh
parameters (adjust the global size and tolerance) Automatic
transitions (make sure the nodes from element to element match up)
Curvature-based mesh Incompatible Mesh option (nodes don't match
up) Mesh Controls (adjust the mesh in specific areas of the model)
Mesh Methods (discussion coming soon in a blog post)So, if you run
a simulation in SolidWorks and get a mesh error that stops the
calculation, that list is where you start to correct the
issue.SOLIDWORKS SimulationHave something to say about this story?
Leave us a comment!Subscribe to BlogTop of FormEmail*
Bottom of Form
Posts by Topic SOLIDWORKS 3D CAD (143) SOLIDWORKS Inspection
(81) SOLIDWORKS Enterprise PDM (28) SOLIDWORKS Simulation (16)
SOLIDWORKS Technical Support (15) Videos (13) SOLIDWORKS World (11)
SOLIDWORKS Training (8) Mobile Devices (7) SOLIDWORKS Electrical
(7)see allLatest Posts 4 Easy Ways to Big SOLIDWORKS Efficiency
Increases SOLIDWORKS Upgrade Sale - 25% Off Ends This Month Hidden
SOLIDWORKS Command Manager? Text in SOLIDWORKS ...easy if you know
how Climb into the SOLIDWORKS TreehouseMost Popular Posts How to
Represent a Knurled Surface in SolidWorks Importing Files Into
SolidWorks How to Easily Rename Your SolidWorks Files and Retain
the References SolidWorks Drawing Templates The Language of CAM
G-Code Tutorial Part 1SOLIDWORKS TrainingSOLIDWORKS Webinars
2015 CADD Edge, Inc | Authorized reseller of SOLIDWORKS 3D CAD
design software and Stratasys 3D printers.
