Why aren't we using AirShaper to do aerodynamic testing ?

[freebeard]

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There will be a toolchain between the data capture and the CFD software to massage the data. Decimation, remeshing and checking for watertight manifold.

[IRONICK]

Originally Posted by aerohead

4) In 2021, the Ford F-150 was analyzed in AirShaper.
5) AirShaper generated a Cd 0.463 for the truck.
6) Ford Motor Company had published Cd 0.404 for that truck.
7) That's a 14.6% discrepancy between CFD and a 'ground-truthed' Ford wind tunnel/CFD value.

I think that AirShaper rounded down, there is no way to get such a value for a dresser-shaped car. Not to be too far from what Ford declare.

[Cd]

At $50 ( fifty dollars ) to run a rough test, even I ( poor, white trash ) can afford a run.
It will give me a much better understanding of where my problem areas are on the car.
I am in the process of re-learning 3D modeling for this very purpose.

No matter if the cD value is off, the test will still be helpful.

Again, you guys are all brilliant mathematicians.
I have a hard time with even basic math, so learning a CFD program is like rocket science for me.

I'm puzzled that only a couple of you guys here have even looked at CFD.

Aerohead, I know you say you don't have a computer.
I literally found one by the dumpster that was a $2,500 + workstation that at the time of it's release was one of the fastest that were on the market at the time ( early 2000's )
So point being, is that computers that can do CFD are now easy to come by for free.
OPENfoam is open source ( free ) software

BTW, This PC I have is over 50 lbs and is a water cooled, dual processor beast. ( So I can't just mail it to you )

Even if old school techniques are better in some ways, I see CFD as yet another way to find problem areas in a design.

[freebeard]

I'm puzzled that only a couple of you guys here have even looked at CFD.

Have a look at this: How to install and use OpenFOAM | Beginner tutorial series #1
Tutorial: Start with Windows and Install Ubuntu Linux and reboot. ???
It appears to be run from the Command line. Ready for that?
Then you write Bash files. Ready for that?

Rabbithole starts here: https://openfoamwiki.net/index.php/OpenFOAM. Note 3.3 foam-extend,

This project is open to community contributions (see Extend-bazaar), none of which get adapted into the official OpenFOAM. Therefore foam-extend has a vast library of capabilities unmatched by the official OpenFOAM project, including (note: this list needs to be revised):

GGI interfaces - useful for rotating reference frames, and stitching together multiple meshes;
groovyBC - allows arbitrary boundary conditions to be specified, without requiring coding / compiling;
newer rectangular matrix solvers' and
pyFOAM - a front end that makes managing OpenFOAM cases easier, i.e. it makes available many features that users of other software suites take for granted, such as:
easily changing the case setup; and
plotting the residuals on a graph as the solver is running.

Writing Python scripts to drive a C++ engine. Got it.

I was a lot closer to a brilliant mathematician before I used paint remover in an unventilated space. What are you doing to re-learn 3D modelling? I have Blender 3.4 running on Apple M1 silicon, but it's on a side table. I need a proper workstation (and a graphics tablet. ...and a good microphone ...and a lens for the HQ camera).

I have a handle on modelling, but rank beginner on editing Geometry Nodes and animation. Geometry Nodes are a graphic tiling interface to Pythion scripting. The Blender Physics engine has a hair system that creates non-crossing streamlines affected by air and gravity.

The reason I think it will be Blender is support for OpenVDB has been in there for a while. That's the field the data is manipulated in.

BTW, This PC I have is over 50 lbs and is a water cooled, dual processor beast.

My World-facing machine is the size of a deck of carrds. But four USB ports.

[freebeard]

I am in the process of re-learning 3D modeling for this very purpose.

I was going to ask, what are you learning. Since I favor free and Open Source I choose Blender. I watched this tutorial from two weeks ago beccause I'm alweays interested in the Explaining Computers channel.

Blender Modeling Introduction: How to create 3D objects!

I learned a few things, how to use a laptop, some snapping stuff, the Preferences Editor window, &tc.

[Cd]

Originally Posted by freebeard

Have a look at this: How to install and use OpenFOAM | Beginner tutorial series #1
Tutorial: Start with Windows and Install Ubuntu Linux and reboot. ???
It appears to be run from the Command line. Ready for that?
Then you write Bash files. Ready for that?

Rabbithole starts here: https://openfoamwiki.net/index.php/OpenFOAM. Note 3.3 foam-extend,

Writing Python scripts to drive a C++ engine. Got it.



My World-facing machine is the size of a deck of carrds. But four USB ports.

Are you familiar with Simscale ? There is a free version that has an easy to navigate U.I. for OPENFoam

https://www.simscale.com/product/pricing/

I'm amazed to see how Blender has progressed over tge years.
Honestly, I cam't see how that Autodesk can still charge thousands ( and by SUBSCRIPTION so recurring every year )
I have an Alienware tower i found by the dump. It was once a "supercomputer", but now is less powerful than my phone i use to type this.
It is such an energy hog that i considered using it as a multifunction heater, but it's not even efficient at that !( Use it as a PC and heat my aprtment with it at the same time. )

I currently have a Surface tablet ( first gen ) that runs my old version of Softimage / XSI as well as Blender.
I also have Blender but have to run an old version because it just wont run anything newer than 2.7
This phone ( a secondhand Note 8) is running Prisma3D.
It's amazing how I'm actually able to model stuff on this tiny phone in my pocket.
I plan to soon get a PC that can run Blender 3.4
I would love to see CFD in Blender.
Thanjs for the video link.

[freebeard]

Honestly, I cam't see how that Autodesk can still charge thousands ( and by SUBSCRIPTION so recurring every year )

Behold the power of free and opensource software. backed by corporations and driven by smarty-pants. There's no was for commercial software to compete.

The big breakthrough was 2.79->2.80. There're experimental forks, long-term support releases and free and paid extensions. It's like the Borg.

[freebeard]

Here's how it happened:

Why is Blender FREE? [story]

[aerohead]

Originally Posted by IRONICK

I think that AirShaper rounded down, there is no way to get such a value for a dresser-shaped car. Not to be too far from what Ford declare.

I don't understand this comment.
Pickup trucks are simply 2-door, or 4-door sedans, without trunklids ( boots ) as far as the automakers are concerned.
The 2013 Dodge RAM 1500 HFE was Cd 0.363, according to Chrysler Corp.
I found my notes from 2014. The Ford F-150 Crew Cab, 4X4, 6.5-foot bed was rated at Cd 0.402.
The current F-150 would be similar, and not 'higher'.
The Ford F-150 LIGHTNING is reported to be ' 7% lower drag ', which places it in Cd 0.3738 territory.
The lack of the ICE cooling system could probably take care of the difference all by itself.
This is 'why' AirShaper scares me off.

[aerohead]

An online search for ' cutting-edge low-drag aerodynamic technology' led to, 'Electric Car Range Drives Race For Aerodynamic Efficiency,' February 16, 2022, by Wouter Remmerie of AirShaper, in conjunction with data by Vincent Keromnes, domain leader, dynamic benchmarking at A2MAC1.
1) 3-D scans of Tesla, meshing, and CFD results were compiled, back-to-back with full-scale wind tunnel tests at the S2A wind tunnel.
2) The AirShaper results overestimated drag by 9.7%.
3) The cost of scans, meshing, and CFD, equaled the cost of the full-scale wind tunnel testing.
4) In the USA, that might equate to $ 4,000 for the 1st iteration.
5) In order to test a modification would require the expertise of someone fluent in CAD-CAM in order to modify the point cloud of the digital model, mesh it, and then rerun the CFD.
6) The discrepancy introduces 'noise' which exceeds the 'signal' resolution of many modifications we might be looking for, 3.5% in this instance.