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I’ve been creating 3D CAD models for almost two decades, always for manufacturing but some specifically for CFD or FEA analysis downstream.

You’ve got all the detail you could ever want but before you can simulate any kind of physics, it needs to be carefully reduced in complexity, regardless of whether you have integrated simulation capabilities or not.

A Formula Racing E car I modeled for a client interested in getting conceptual design proof

There’s often a lot of friction here in many respects – I used to become really anxious at times as an Engineer responsible for this “clean-up” process.

You have colleagues waiting on you expecting it to be a clean, ready-to-use model, Managers expecting you to avoid delaying development and Customers / Clients wanting to make grounded decisions fast.

And I’ve had to think deep and hard about this workflow throughout my career as a Senior Mechanical Engineer – often without a good answer to the problem.

The issue is partly due to the discontinuity between the tools, file formats, technical capabilities and poor communication.

What a CAD model really is…

A streamlined racing bike handle I developed a few years back.

Years ago I was a young, budding Engineer without a clue. At University, I got introduced to the Engineering tool “stack” – CAD, CFD, FEA etc.

At that time I saw everything at face value – CAD was for modelling the design, FEA virtually tested the structural strength / loads and CFD was there to investigate how the fluid behaves through or around the design.

I was right…but mostly wrong.

After more than a decade in industry as a Senior Engineer, I’ve come to the conclusion that a CAD model is really a single source of truth for most Engineers and Teams. A CAD model:

  • Is used to capture design intent

  • Is used to describe the physical shape, size and dimensions

  • Is used to describe manufacturing details needed

  • Often contains META data for use by other Engineers, Clients and even Marketing

But a CAD model in itself is just geometry and practically useless when it comes to simulation after it meets all of the above.

CFD tools like OpenFOAM expect watertight, triangulated geometry with labelled face regions before you can apply the all important boundary conditions to them.

The frustrations of dealing with this humble you over the years.

“Nasser, how much detail do I need to keep?”

I got questions like this throughout my career and the truth is it’s not always straight-forward but there is a method and workflow that makes it far easier.

An oil rig model, simplified but as required for downstream simulation.

And it all depends on the complexity of the design and what you hope to extract from your CFD simulation results.

An understanding of the meshing and simulation process helps to build an intuition for these things too.

With that said, stripping away model details without a careful and diligent workflow with this in mind will risk large amounts of wasted time, errors, mistakes and frustrations, affecting the downstream simulation setup and solve processes.

A clear framework that stopped me guessing…

The most challenging environment for an Engineer is industry.

Complex consumer product – it has all the fine details but too many for a clear and focused simulation study…

It’s messy, you’re up against tight deadlines, communication is poor and nothing quite works. Iterations become your teacher.

I’ve spent my working career (16+ years) modelling, editing and deleting all kinds of features from all kinds of CAD models destined for simulation internally or using external consultants.

I’ve built a personal framework to remove the guesswork from this process and can now confidently prepare any model, regardless of complexity, for CFD simulation.

It has served me consistently and now you can use it too to save you time and frustration!
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