Mythbusters tests "golf ball" dimples

[Nathan jones]

It seems that member title is awarded by post quantity not content...

[Piotrsko]

You might change it to some personal message like I did but I forget how. It's in the User CP but could be a minimum amount of posts and I have found a lot of options here are browser dependent. Worse case use chrome as a default.

[aerohead]

Originally Posted by Nathan jones

..

N.b And I'm not a Master ecomodder, who changes this??!!

* You'll be a 'master' soon enough!
* With the two images and 'qualitative' results:
It seems like the left image should depict a 'full' square-back wake, encompassing the entire rear of the structure.
The image to the right seems reasonable enough to a point.
The separated flow would arc down along a virtual 'golf ball' path, then, when it reached beyond 22-degrees of downslope, 'explode' into turbulence.

[freebeard]

I'll repeat the question.



Is the ground plane to the left? Is it a centerline section? What gives?

[aerohead]

the wake for the shape on the left should look like this,
http://https://ecomodder.com/forum/m...here-money.jpg

[Nathan jones]

Originally Posted by Piotrsko

You might change it to some personal message like I did but I forget how. It's in the User CP but could be a minimum amount of posts and I have found a lot of options here are browser dependent. Worse case use chrome as a default.

Thanks, I tried but it means filling stuff out, when I've got time I will do it

[Nathan jones]

Originally Posted by freebeard

I'll repeat the question.



Is the ground plane to the left? Is it a centerline section? What gives?

Not everything is free. Try creating your own cfd enviroment, model some ideas and share them around

[aerohead]

Originally Posted by freebeard

I'll repeat the question.



Is the ground plane to the left? Is it a centerline section? What gives?

1) The ground plane is out of sight, below the two images.
2) Flow is from the left, to right.
3) It may be 2-dimensional flow. Don't know.
4) For the left image, it's right ( downwind ) surface should be in total turbulence.
5) It's similar to the original Ahmed body on stilts, from around 1982.

[Nathan jones]

Originally Posted by aerohead

* You'll be a 'master' soon enough!
* With the two images and 'qualitative' results:
It seems like the left image should depict a 'full' square-back wake, encompassing the entire rear of the structure.
The image to the right seems reasonable enough to a point.
The separated flow would arc down along a virtual 'golf ball' path, then, when it reached beyond 22-degrees of downslope, 'explode' into turbulence.

Thanks, but the hardest work was not done by me. I just used it for my car, and I think they do work for already laminar flat areas.

A small improvement, surface area, mass and driving style still hold far more areas for increased efficiency.

[aerohead]

It does seem to be the case.
The only explanation I can come up with is that, the dimples 'DO' act as some form of VG, creating a lower local pressure along the 'boundary'.
With respect to the Mythbusters Ford sedan, they were able to induce the turbulent boundary layer to remain attached a bit better, minimizing the existing separation bubble, allowing enhanced flow reattachment, with higher pressure at the inevitable separation line.
Base pressure was slightly increased.
Pressure drag decreased.
Total drag reduced.