getting my Si slippery

[MetroMPG]

Originally Posted by Christ

So what is the purpose of dimpling metal panels to increase aero?

For cars? See here and here .

[MetroMPG]

Dichotomous: FYI your car does not have flow separation on the upper roof surface where you have placed the bumps.

[dichotomous]

Originally Posted by MetroMPG

Dichotomous: FYI your car does not have flow separation on the upper roof surface where you have placed the bumps.

would you like to tell that to the snow and water that dont get air scrubbed off there while they get scrubbed off everywhere else?

though I hear what you are saying, and looking at the pictures and car I have no idea WHY it would do what it does there, but it does. maybe its the moonroof weatherstripping thats just barely above to the surface? it SHOULD stay on, I fully agree with that. but it doesnt seem to by evidence of the nonscrubbed top.

if it is the weatherstripping I think maybe something to break into microturbulance (smaller than the bumps) either rightbefore or after might be better.

[MetroMPG]

Maybe you're seeing the effects of a thickening boundary layer, but it's highly unlikely you have significant flow separation, even from the weatherstripping.

I have a feeling we're just talking at cross purposes over a definition.

Head to Wikipedia or search EM for distinctions between laminar vs. turbulent vs. separated flows.

It's important to get the terminology right or it muddies the waters of the discussion.

[dichotomous]

Originally Posted by MetroMPG

Maybe you're seeing the effects of a thickening boundary layer, but it's highly unlikely you have significant flow separation, even from the weatherstripping.

I have a feeling we're just talking cross purposes over a definition.

Head to Wikipedia or search EM for distinctions between laminar vs. turbulent vs. separated flows.

It's important to get the terminology right or it muddies the waters of the discussion.

so are you thinking that they are just in the way and creating drag when the flow hasn't seperated and created a lower pressure area, just a thicker (but still good) boundary layer? I'll admit to being sort of confused about that.

[Christ]

Originally Posted by MetroMPG

For cars? See here and here .

Nope. Golf Balls. :P Thanks.

[aerohead]

If I estimate your Honda at Cd0.30 and 19-Ft square frontal area,then to reduce the drag at 60-mph,to that you now experience at 40-mph,would require you to drop the Cd to 0.133.---------------

You're talking about a Ford Probe-V Concept Car.----------------

To do that would require complete skirting of all wheel wells,sealing the front of the car with relocation of the radiator and A/C condenser to the rear quarter-panels,a completely smooth belly-pan,and recountouring and extension of the roofline and rear windshield.---------

You would also need to do active- suspension,where you could lower the car at speed for highway driving while modifying its "rake" for optimum drag reduction. A very ambitious project! -----------------

If you can settle for Cd0.17 and a little less mpg,follow basjoos and what he's done to his AeroCivic.

[dichotomous]

yeah, the wife saw basjoos' car, she said if I did it nicer than that she would ride in it, kinda like the prius photoshop on this site somewhere.... I thought that was kinda funny.

a completely new hatch is how I would do it, the whole thing would lift up. thats a BIG if. but I think I could get lower than basjoos because of the overall starting shape of the car. I just dont know that I want to go that far, not yet at least

[dichotomous]

well, it was snowy, but not so snowy where I "needed" to brush off the car, so I didnt. drove in, hit 65mph once, generally it was 40mph with 50mph on the interstate (aside from the aforementioned following cars up to 65mph). it was very windy in the cross and spin wind situations, the whole way.
took a picture of the rear of the car afterwards.

what can we tell from this? I welcome all analysis' and will entertain all ideas.

more background: the wing trailing edge has been dropped a little more, maybe another half inch from previous, played with the holes and bracket and got it down as far as I can so far. I also duct taped over the transition from mount to wing, its smooth now.

my initial analysis: appears that there is either much thicker boundary layer over the back of the wing mount down to the trailing edge, or the flow may seperate a bit, or at least its a lower pressure and lower flow area, as evidenced by the snow that goes smoothly from the wing edge to the mount start. there is also evidence on the sides that large vortex's are forming off the mount uprights, since the snow is scoured clean there. the top buttons appear to be working, as normally there would have been snow up there, but its not there now. maybe I will take half of them off (just one side) to show this better or disprove it to my own flawed memories, good test at least

[dichotomous]

possible epiphany: what if the snow thats stacked up is from a "snow fence" situation with the upper bumps, the mount uprights might not generate vortexes that early, but the width of the snowpack is about as wide as the bumps further ahead.

thoughts appreciated