Grooved surfaces

[thmas]

I've just been watching Africa on BBC iplayer. Featured was a large whale which had a grooved area of skin around its lower body. It left me wondering if there would be any aero benefit to having a grooved surface to channel air around the cars surface into key areas such as the rear floor? Or would this simply create unwanted drag?

[PlatinumZealot]

Yes there would be less skin drag under the floor if it had a multitude of lateral grooves under the floor... Correct me if i'm wrong though.

[flynfrog]

poor surface finish and increase in surface area always decreases drag that's why its so popular.

[wesley123]

Yes there would be less skin drag under the floor if it had a multitude of lateral grooves under the floor... Correct me if i'm wrong though.

Why the hell was this post rated -1?

But yeah there probably would be less skin drag, but on the other side the floor would generate less downforce too. Would be more useful on an road car than on an f1

[flynfrog]

Seriously how do you think there would be less skin drag? Increasing wetted area almost always results in increase in drag.

what if you had groves, golf ball dimples, and vortex generators you could have - drag then right?

[Tommy Cookers]

Yes there would be less skin drag under the floor if it had a multitude of lateral grooves under the floor... Correct me if i'm wrong though.

Why the hell was this post rated -1?

because the OP was asking about longitudinal grooves ?

longitudinally grooved film has been trialled in-service by Airbus ?
(for reducing drag by reducing thickening of the boundary layer)
similarly, dolphins etc have a porous skin top layer
(the whale grooves are primarily for anatomical function, though ?)

regarding DF etc, the OP sounds like a good question to me

[thmas]

I was thinking if the cars body panels had surface groves similar to the organic groves of the whale, directing air flow over the side pods and around the top air intake. I'm not sure if this is against regulations or would be beneficial in anyway?

[No Lotus]

The grooves on the lower surface of the whale, peculiar to the "rorquals", are to allow the mouth and throat of the animal to expand when it takes in a gulp of sea water prior to straining. They probably don't serve a hydrodynamic function - or at least didn't initially evolve for such. However, very small grooves oriented in the direction of flow have been shown to be beneficial in stabilizing the boundary layer and in reducing drag. They were used on "Stars and Stripes" in 1987, for example, to win the America's Cup. In that case, 3M provided Dennis Connor's team with a specially designed grooved tape that was applied to the hull.

Concerning dimples, there's no question that, properly placed, they'd serve to decrease drag on an F1 car. I have assumed that we don't see them because of regs.

[turbof1]

My vision on it is that when the car runs straight it has a beneficial effect due the boundary layer (compare it with a gulf ball). However, I believe, could be totally wrong on this, that in wake it brings disadvantages due airflow not going straight into the grooves and thus the boundary layer breaks up.
Compare it to the gulf ball: long shots where enough force is applied to get aerodynamics come into effect, the ball is stabilized due the dimbs. Wind will have much less effect to get it diverted from its trajectory. HOWEVER, that also means turning the ball is very difficult. A gulf ball played under a long shot does not need redirection midair, but a f1 car needs to turn as fast as it can.

[amouzouris]

I carried out a CFD test to try and answer the question. If grooved surfaces with either longitudinal grooves and lateral grooves will reduce drag.

The body has a teardrop shape, it is 320 mm long and 100 mm thick on its thickest part. I tested it at 42 m/s and found the drag produced by each body.

Ungrooved body:

Drag: 0.27 N





Longitutinal Grooves:

Drag: 0.95 N

As Tommy Crookers suggested the longitudinal grooves reduce the thickening of the boundary layer. Because of the increased surface area the body produces much more drag.









Lateral Grooves:

Drag: 3.68 N

The drag increased too much here partly because of the grooved shape of the front of the body.











Lateral Grooves V2:

Drag: 2.57 N

I smoothed out the front of the body that created a lot of drag, but still the drag figure for the body with lateral grooves is too high.







http://technicalf1explained.blogspot.co ... -test.html

[turbof1]

I would like to see the effects on the boundary layer if the shape was flat and the longitudinal grooves were less pronounced. IMO, the grooves should have a positive effect on the boundary layer.
Amazouris, I was just studying the pictures; I am going to take the normal and longitudinal grooved teardrop shapes out of it for direct comparison:




I noticed a pressure drop in the left side in the "ball-section" (compare the darkest blue areas). I was thinking of a more complex shape to play with that. Could you perhaps modify the teardrop shape like this: the bottom half of the teardrop fully grooved, the upper half only grooved from the widest vertical diamater point, completely to the right (with smoothened transition)

[amouzouris]

I would like to see the effects on the boundary layer if the shape was flat and the longitudinal grooves were less pronounced. IMO, the grooves should have a positive effect on the boundary layer.

I agree that the grooves are too deep..but i think that it would still have a negative effect...because they are grooves! not dimples!

[turbof1]

I edited my previous post. Please check that out. I think I am asking something difficult, though I would very much like to see the results of that. I am also correct to assume that the fully lateral grooved teardrop creates vortices at the tail?

[PlatinumZealot]

Seriously how do you think there would be less skin drag? Increasing wetted area almost always results in increase in drag.

what if you had groves, golf ball dimples, and vortex generators you could have - drag then right?

Nope.. you are DECREASING the area. think very carefully about it...

[PlatinumZealot]

I carried out a CFD test to try and answer the question. If grooved surfaces with either longitudinal grooves and lateral grooves will reduce drag.

The body has a teardrop shape, it is 320 mm long and 100 mm thick on its thickest part. I tested it at 42 m/s and found the drag produced by each body.

....

What about the relationship between your groove depth and body size? (length width etc).. what about the profile of the grooves? sharp round etc...