Mobius

iTrader: (2)

I have decided to see what progress I can make with CFD analysis of an NB miata. After much m.net forum searching of necro threads and related google searches, I have decided to go with Sketchup. There are existing NB models in the warehouse, and there is a complete openfoam plugin to run the CFD on the model. Now I realize saying it like this is essentially saying
1. get sketchup model and openfoam plugin
2. ???
3. CFD Profit.

There's a lot between actually getting the software and getting results which are at all viable. I'm aware of that.

Issue #1.
This is the model I am starting with: 2004 Miata in 3d warehouse. From what I can tell, all of the NB models in sketchup were started from same set of 3-views, the only ones I could find online for an NB, located here: 2004 NB 3-view from blueprints.com

The issue I want to fix is that the 3-view, and correspondingly the models built from them, have a rise in the pinch weld line from the rear to the front. It should be flat. When looking at the model in sketchup the lower edge of the side of the car behind the rear wheel is a good 2" higher than in front of the rear tire. This is going to affect our airflow analysis, yo!

What I want to be able to do, and what I cannot figure out how to do, is to grab that bottom edge, and stretch it so that it's parallel to the ground.

I have tried using the fredoscale and joint push/pull plugins without success. I have tried exploding the components as far as I can, in hopes of being able to grab vertices and manually reposition them, but no luck there either.

I admit I am a scrub bench-warmer to all of this. Anyone got pointers or ideas on how to fix the model?

Full_Tilt_Boogie

iTrader: (1)

I didnt realize there was an open foam plugn for sketchup. Im very new to it as well.

Now I very excite.

Mobius

iTrader: (2)

Khamsin, a Sketchup plugin for CFD analysis.

Yes, be excite!

Edit: is not free, may cause detumescence.

Leafy

iTrader: (1)

I tried to use sketchup to do a room arrangement once for my parents when i didnt have a real cad program handy. I could not for the life of me figure that damn program out. It feels like the saab of cad programs, aka made by some dudes who saw this cad program one time when they were drunk and thought it was a good idea. Its like old inventor 6 and pre-windows 7 paint got pregnant together then paint gave inventor a coat hanger abortion in the 3rd trimester.

If someone actually knows how to use sketup, I too would love to hear it for the times when I somehow dont have access to a cad program anymore.

3rdCarMX5

iTrader: (1)

Sketchup fails when you try to use it like Solidworks. It is not a dimension critical program.

I learned on Solidworks and then went to work and needed free software to mock something up for the machinist. It took a good day to realize Sketchup is not Solidworks. It is still great, you just need to change the way you make models. A lot of line chopping, and getting stuff close enough. If you don't dimension something and just move it joined to something else, the dimension will be off. 2mm becomes 1.8mm.

Sketchup is how an architect in a developing country makes a project presentation, or a college student makes a diagram for a poster.

Leafy

iTrader: (1)

That sounds exactly like what I was running into. So Sketchup was not the droid I was looking for.

Mobius

iTrader: (2)

I also have a (legal) copy of Alibre, but I'd have to make a model from scratch. Then export it to something to run CFD on.

Leafy

iTrader: (1)

You could still export it to open foam. Just need to do it as an STL and then use an STL to mesh converter. You should see what filte types you can get sketchup to export to see if there's one you can open in alibre.

Mobius

iTrader: (2)

Although I don't need sub-mm accuracy. At least, I don't think I do. If the proportions are all correct and in scale with each other then that should be good enough. This is Rocket City Redneck aero analysis, after all.

3rdCarMX5

iTrader: (1)

It better not be, I hate that show. Would be so much better if they played it straight. Their editor/director needs to be sat down. It doesn't all need to be dumbed down.

"We made a Papa John's Pizza delivery bike, herp dee derp da dump. I done did it."

Dlaitini

I use Blender for 3d modeling... I have been trying to get a plugin to work that will allow me to use a Kinect camera(s) and take multiple shots around a car to create a point cloud to use as a basis to model a surface off of.

IIRC it can inport/export to sketchup. what type of file format do you need for the flow dynamics program?

Leafy

iTrader: (1)

If you have a jesus phone you can download the 123d app from autodesk that supposedly will 3d scan something and make a solid model. Unfortunately there isn't an android version of the app yet.

Dlaitini

Sadly no, I am stationed in Okinawa, and when I got here au was the only ones that you could depend on to get a signal on island and they only had Androids.

When I get home will check to see if the app works on the iPad thou

I do have 123d sculpt program they have.

Mobius

iTrader: (2)

Wife has a 4s. Hmm.

Dlaitini

well since it looks like they will be have already cracked the 6.01 OS, i have upgraded to it as it is required for that scanning program to work.

I work nights here, (10pm-6am) so i got up today after the sun had gone down. Once i get registered to their system, i will test with the skyline as soon as the sun comes up.

This will be mainly for a test, and to see if i can get the file format so it can be transfered.

Im looking to see if blender has any CFD plugins too, or if they just use the built in liquid/smoke

Dlaitini

Yeah, intresting program, but I am guessing since it works with looking for common detail across several pictures, you have any reflection on anything , since that reflection moves across the different images it borks the 3d model it produces

model ended up having holes everywhere and was very lumpy.

I am going to keep trying with the kinect, the sensor that puts out the point cloud will not be messed up with shiny surfaces.

Dlaitini

Ok so an early render of 4 small snapshots stitched together using the Kinect software and laptop.

I think this will work well to use as a base and make a much simpler model.

This is close to 1 mill polys but it also has lots of overlap between the front 3 snapshots I took, and I need to figure out this software so i can do more then 1x1x1 cubic meter at a time.

Hopefully I can figure it out so I can start at the front and it will let me do a complete walk-around the car as it adds the surfaces in.

The Kinect sensor goes right thru plastic/glass, so it got the interior of the left headlight, while the right headlight is hazed over. I guess can use that to advantage, and when doing a better quality scan, will have to cover the windows and lights in tape so it can figure out the surface better.

Mobius

iTrader: (2)

That looks good. I have a kinect, what's the software doing this?

Dlaitini

http://reconstructme.net

I have been trying to bump up the size of scanning area I can do at one time.. it seems the resolution goes down as I do this, so will have to mess with things a bit before i can figure out a good balance.

It was picking up all the undercar detail too, so can maybe see whats going on there too

A few people on their forum also say that it goes crazy if you are doing any large flat areas like the hood or roof.. some have put little ***** of blue tack for it to use as a reference point(s) and to line things up later