The Tuft Test Images Thread

[Vman455]

Originally Posted by jakobnev

If the flow is upwards over the rear windows, could it be creating trailing vortices?

I think so. If you look at the first two images, it's kind of hard to see but the tufts at the outer edges of the window vibrate faster and to a larger degree than those in the center. I suspected this meant faster flow there, and when I measured pressures on the window, sure enough the pressure was lower toward the outside. Fitting the lip spoiler raised the measured pressure, but it is still lower at the outside than center, so my next step will be to fit fins (similar to what JulianEdgar had supporting his wing) to disrupt vortex formation--and then tuft the window and measure pressures to see what that does.

I actually sketched out something similar to that image the other day in my "things to test" notebook!

[jakobnev]

It would fail. The refractive index would make it opaque at that angle.

It's meant to be horizontal* so you don't look through the material at all when looking straight back, only if you were looking backwards sideways in the silly way, would it be in the way.


*) Nearly, you could make it the same angle as from you eyeballs to wherever on the rear window it starts.

[Cd]

Here is a tuft test I did when my family came to visit.
Just my luck, she had the setting on low res. This first one has the speed changed a bit. She had it set on slow motion https://youtu.be/KVBkjLsD8jc
Here is a slow motion version of the same :] https://youtu.be/dATOXSCUbDM
And here is the test without covers over the side lights : https://youtu.be/JFEDUjEvpyI
Here is the same car. It is stock, but ( unlike the above tests ) I had the mirror pulled back.
Of note, is that despite the smooth hub caps, there is a lot of turbulence around the wheels. Compare with the video above. https://youtu.be/ibXI_8S6hTc

[Cd]

Why can't I post links on Android ?

Will this work ? : https://youtu.be/dATOXSCUbDM

Nooope

[Vman455]

The last video link works.

Interesting that the flow behind the front wheels is attached (and not very turbulent) while behind the rear wheels it's almost completely separated. (It looks like one tuft is stuck, but the others sometimes point forward). Also separated flow behind the mirror; I wonder what another mirror shape would do?

[Cd]

Originally Posted by Vman455

The last video link works.

Interesting that the flow behind the front wheels is attached (and not very turbulent) while behind the rear wheels it's almost completely separated. (It looks like one tuft is stuck, but the others sometimes point forward). Also separated flow behind the mirror; I wonder what another mirror shape would do?

BTW, The links might work now. I removed some of the text

Oh good. I'll link the others.
The area behind the rear wheel is in turbulence because of the steep angle, but also the fit and finish of the piece.
There is a high region thst the air is tripping over. ( the tuft that points upwards just behind the light. )
I rushed to install it, and it shows.
I have to get to bed, so will post more tomorrow.

EDIT : The links might work now. I removed some text.

[M_a_t_t]

Here's the video embedded.

https://www.youtube.com/watch?v=dATO...nnel=monkeyboy

The outer strakes of the diffuser looked like it could be better, other wise I like it. Is there a hole in the top of the extension? Interesting paint job btw. Previous owner or was it done by you? Have you had any trouble with L.E.O. for the clear part for the lights? I'm probably going to add an extension and haven't quite decided what I want to do with the lights.

Is this the same car?

https://www.youtube.com/watch?v=mmsP...nnel=monkeyboy

[freebeard]

Shark mouth!

[Cd]

I spent around 20 min this morning replying to this , but it didn't go through, so I'm going to copy paste your questions:
The outer strakes of the diffuser looked like it could be better, other wise I like it.

Yes, the flow is awful back there. Nothing was entiely finished at the time of this test.
The diffuser only goes to the back of the gas tank, and I didn't have the underside panels installed.
The extention also was not fit well during the test, and there was a protrusion that was causing turbulence ( the tuft behind the wheel that is flowing upwards. )
I also didn't have a complete gap filler installed on the back sides of the wheels.
It was just open, and I had a bit of tape on the front side.


Is there a hole in the top of the extension?

If you mean to the left and right of the area just past the 3rd brake light, yes.
I have it open so that air has a way to escape if a sudden gust tries to tear it off, or bust the back window in the process.
During the test, I noticed tufts placed inside the Kammback flowed upward through the hole.

Interesting paint job btw.

I figure if people are going to stare and post pictures, I might as well make it useful for me and advertise my art.
People started calling it the Batmobile, so I thought what the hell. I'll play that up a bit.
( I added a small tail section like you see on bats )
Why is it that people see aerodynamic cars as looking like a Batmobile ?

Previous owner or was it done by you?

I'm the fool that did it. It used to be a really nice car


Have you had any trouble with L.E.O. for the clear part for the lights?

What is L.E.O. ?

I just had the clear pieces on for the test. In fact, they were just duct taped on, and removed moments later.
I don't drive with them on, because eventhough they are clear, the reflections and glare prevent you from seeing the lights fully.
They showed good attached flow, eventhough they are at the same angle as the strakes.
The other video has them removed.
Unfortunately, the camera was set to low res for that video.

I'm probably going to add an extension and haven't quite decided what I want to do with the lights.

For now, I may just create an air ramp.

Is this the same car?

Yup ! It used to be a really nice car.
Have a look at the turbulence around the wheels in the old video, compared to the new version with wheel gap fillers.
The air is quite a bit smoother.

[freebeard]

What is L.E.O. ?

Law Enforcement Officer[s]?