sharkskin aerodynamics

[phord]

Had any body researched onsharkskin aerodynamics?

[Bicycle Bob]

Sharks use microgroves paralell to the flow to help stabilize laminar flow. It works well enough to be banned from Olympic rowing shells. However, on a car, it would often be defeated by crosswinds, even if we could save it from all the other things that make laminar flow on cars pretty much an academic fantasy.

[aerohead]

For a submerged body almost all resistance can come from viscous drag at the "skin," as in a torpedo or submarine.
For automobiles,the contribution of skin friction is on the order of 7-12% of total drag,whereas profile drag is on the order of 55%.
Space utilization basically defines the "size" of a vehicle,and it's surface area.
And for commercial coatings as used on autos,laminar boundary layers cannot be maintained above about 20-mph.
Compliant viscostatic coatings which might produce the diaphramic fluid damping exhibited with shark and dolphin skin could theoretically reduce a car's skin friction,but the weight/inertia penalty might over-shadow any gains.The coating would also be required to survive without ablation,for 100,000 miles of driving.
Consumer acceptance of the skin's "styling" could also prove to be a hurdle.

[Bicycle Bob]

Laminar flow first escaped from the lab when Bondo was invented to cover the rivet heads on the wings of the P-51. After refueling services resumed in Berlin, general aviation found it too much trouble to maintain. However, it had no particular speed limitations up to compressibility, a separate issue. Once we get form drag and induced drag down to half their usual values, me might try increasing the laminar flow area, but given the presence of front wheels, I doubt that we'd get past 30%, for a 15% reduction in skin drag, or maybe 5% overall. That part of the body would probably have to be a seamless unit, on which you could not feel the headlights.

[mchlbk]

Who cares what the public thinks, we're ecomodders!

Personally I'd love to own a golf ball-dimpled car like the one from this Mythbusters video: VIDEO: Mythbusters test golf ball-like dimpling effect on fuel economy (*Spoiler Alert!*) — Autoblog

The car went from 26 mpg to 29 mpg after the "dimple implementation". Perhaps using a dimpled surface for high pressure areas (+ belly pan?) would benefit mpg.

[Bicycle Bob]

Cars are shaped more like the "thick wake" above, so they keep the flow attached without dimples. I don't know how mythtbusters got their gains, but better driving seems likely. Dimples and other vortex generators are a way to help a bad shape, not something to plan on using. In the second illustration above, the laminar boundary layer should end at the first dimple encountered.

[cfg83]

Bicycle Bob -

Originally Posted by Bicycle Bob

Cars are shaped more like the "thick wake" above, so they keep the flow attached without dimples. I don't know how mythtbusters got their gains, but better driving seems likely. Dimples and other vortex generators are a way to help a bad shape, not something to plan on using. In the second illustration above, the laminar boundary layer should end at the first dimple encountered.

Is it *possible* that golf dimpling might aid wheel covers? I ask because a wheel cover is rotating like a golf ball. Or am I just being a goof ball?

CarloSW2

[Bicycle Bob]

I'd say "wishful thinker." Even if your hub caps were shaped like half balls, the tire shape would be providing plenty of turbulence.

[alohaspirit]

Originally Posted by mchlbk

Who cares what the public thinks, we're ecomodders!

Personally I'd love to own a golf ball-dimpled car like the one from this Mythbusters video: VIDEO: Mythbusters test golf ball-like dimpling effect on fuel economy (*Spoiler Alert!*) — Autoblog

The car went from 26 mpg to 29 mpg after the "dimple implementation". Perhaps using a dimpled surface for high pressure areas (+ belly pan?) would benefit mpg.

2 threads got started on this topic. Here ya go

Mythbusters tests "golf ball" dimples

Mythbusters "tests" efficiency of dimples vs. smooth, and clean vs. muddy car

[ChazInMT]

I have thee COOLEST picture of sharkskin close up EVER! (OK, now WE have.....ain't the web grand?) I use this photo as the wallpaper on my cell phone I like it so much. I think it's astounding how these shapes evolved naturally on sharks. It looks like an invasion of alien fighters. On mans best day he would never think to do it like this!

I guarantee you like this one.




Credit to "Eye of Science" eye of science Click "English"/ "Gallery"/ "Technic" then "Image 2" for more details.