Shrinkwrapped & Turbocharged

Hey there,

It’s Robin from CFD Engine & it’s all about serendipity this week.

A week in which a long-standing client asked if I could tackle a project with an impossibly short timeline.

And also the week in which I discovered that shrink wrapping is in the next version of Rhino.

Perfect timing – Could this be the tool that enables this project? 🙏

A little context

I hope you’re luckier than me & that your projects don’t start with an overly-complex CAD model, featuring dozens of parts that you don’t really care about, but can’t ignore.

For example, in a racecar project I can’t ignore the engine & gearbox, but I don’t need the level of detail that’s in the CAD. I can’t leave it out & I can’t leave it as is.

And so the journey begins – closing holes, removing internal details, filling the gaps left by missing seals, fasteners & gaskets. Generally just trying to remove the spots where snappyHexMesh might hide a “surprise” for the solver.

I’m used to this workflow, but it takes ages & this project deadline is short-short, so…

“How can I do a month’s CAD clean-up in a week?”

Shrinkwrapped

You’ve seen things shrink wrapped in plastic before, well this is the CAD version. Quickly wrapping a simple mesh around a complex model so that it’s broadly the same size & shape, but with a fraction of the detail. Oh & it’s watertight too.

There’s a trade-off though.

What you gain in speed, you loose in sharpness. Shrinkwrapped models tend to have soft edges. Not a problem in my case where I’m looking for volume/blockage to add to my model, but not suitable everywhere.

I know that shrinkwrapping can be a huge time saver, but I’ve not had a good way of doing it, until now – enter Rhino v8

Rhino v8

McNeel (makers of Rhino) have an interesting approach to development. As a license holder for the current version (v7) I can use the next version for free whilst it’s being developed. A sort-of closed beta where I can try out all of the new features & help them with their testing.

So this week I’ve been trialling their shrink wrapping tool & I reckon it would be a great addition to any CFD toolkit.

You can wrap CAD, meshes, or even point clouds, it’s pretty fast & it’s really easy to use / play with.

It comes with some extra “nice-to-have” features too, like polygon optimisation to reduce the mesh count, hole filling, smoothing & the ability to offset the wrap to produce inner/outer surfaces.

It seems to be good at detecting & closing circular holes, but perhaps not so good at irregular openings.

It’s also not great at capturing sharp edges (unless you turn the edge-length waaay down) but then neither is snappyHexMesh so I’m not that worried.

It is a bit “crashy” though 🫢 hopefully that will all be fixed by the time it’s properly released.

Check out this video to see a 70sec demo of all of the main features.

In conclusion

I’m always a bit reticent about sharing yet another new tool, especially one that you have to pay for & that you might not have access to 😕 But I think this one could be a huge timesaver for some of you & another good reason for me to recommend Rhino to CFD people.

Can it do a month’s CAD clean-up in a week? I’m not sure, but it’ll certainly help.

Have you got any major mesh-prep time savers that I should be looking into?

Should I do a “How to wrap stuff in MeshLab” email at some point? It’s a bit harder to use than the Rhino version, but it can work & it’s free 🤷‍♂️

Let me know.

Until next week, stay thankful 🦃