English

# What happens when you mesh: OnScale Solve’s simple answer

By Marshall Williams 23 August 2021

Last time, we introduced the star of simulation most designers have a love-hate relationship with: meshing. We established that mastering meshing requires the fervent eye of an artist and the lucid logic of a scientist. But, you may be wondering, what happens when you mesh?

OnScale is in the business of making all engineers masters of the design process. Understanding meshing is a great first step towards mastery of iterative design, and we hope that this article is the start!

### Have you wondered what’s really happening when you decrease the coarseness of your mesh?

The very simple answer is, cell size decreases, increasing the number of total cells whereupon simulation calculations take place, reducing the error of the results relative to reality.

Wondering what any of that means?

Let’s dive into these concepts! (And keep the original question in mind!)

### Meshing: “Dummy” CAD to Computational Canvas

In FEA you have two fundamental things, physical geometry and computational geometry. Meshing is the means by which we transform a physical geometry into a computational geometry.

Meshing transforms physical geometry, a “dummy” three dimensional CAD, into a computational geometry, a object made of immense numbers of polygons, to which we can assign loads, boundary conditions, convections, flows, etc..

This transformation involves a few parameters: A certain number of Cells, Cell Size, Coll Gradation (distribution of sizing), and Error.

### Cells, Computational Geometry’s DNA

In the same way that DNA is the genetic blueprint governing physical responses, Cells give us unambiguous insight beyond CAD’s physical characteristics, to numerically solve the differential equations governing our designs’ dynamic responses to physical stimuli.

Meshing starts by breaking up the CAD’s physical geometry into cells: discrete shapes making up the computational geometry. Whether hexahedrons, tetrahedrons, triangles, or quadrilaterals, cells’ shape dictate the efficiency and accuracy of meshing’s translation of physical parameters into actionable computational spaces.

Cells come in different shapes, and different sizes.

Cell Size determines the size of our cells across a given geometry. That one’s easy.

### Cell Gradation, say goodbye to manual cell size distribution

Have you ever had meshing errors due to thin sections of parts or fine details that a mesher can’t correctly capture? Then had to manually address the cell size across every single one of these areas?

There is now a way to mesh where instead of manually addressing each sensitive section, the mesher automatically sizes down the cells in areas where a more fine mesh is required for an accurate computational geometry.

We call this Cell Gradation. And OnScale Solve automates that. That is the beauty of OnScale Solve’s mesher, the cell gradation, the attention to detail around sensitive sections of your CAD is already handled.

Since our mesher automatically creates an ideal distribution of cells, you have full control over error.

Error is a measure comparing a mesh to reality; it is a measure of how closely the mesh represents your CAD.

There is no point in spending extra hours, yes hours (or even days), running a simulation with a dense mesh if a coarser mesh will give you the results you need to take action! The relationship between error and compute time faces diminishing returns very quickly.

### So, remember our original question?

Now the answer should make much more sense! Let’s think about it: cell size decreases, number of cells increases, error goes down. We know what happens when you mesh in OnScale Solve, but what does it imply?

Well, that means that traditionally the accuracy of your results hinge on your compute power and time availability, not your design needs. Simulation should not hold your workstation hostage and freeze your creative moment.

What if there was a platform where you could simulate and obtain the results you needed in a timely manner; with nothing more than a passing thought to compute power and the limitations of your machine?

### The Software

OnScale Solve is that software; web-based FEA with the computation taking place on high powered computers in the cloud. With Solve, you can run massive numbers of full 3D multiphysics simulations in parallel to create true digital prototypes, accurately represented through meshing.