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[Gaffers]

Interesting read about tests being conducted with mako shark skin to reduce flow separation.

https://www.independent.co.uk/news/science/mako-shark-skin-faster-aircraft-a8806681.html

Also, the fastest car is now a milk float.

https://www.bbc.co.uk/news/business-47418405

[Kevin Wood]

Hmm. A shark skin glider would be cool.

[Gaffers]

Hmm. A shark skin glider would be cool.

Surely you would still want normal surfaces on the underside of the wings so that the drag helps create the high pressure for the lift.

[Kevin Wood]

I'm not sure the drag helps anything (well, parasitic drag, at any rate. Induced drag is an unavoidable cost of creating lift.).

My understanding of lift is that it results mainly from the lower pressure due to faster moving air over the top surface of the wing. I'm not sure you need to exert drag on the air below the wing, although inevitably you will.

Controlling where the flow is laminar and where it is turbulent is important, though, and "shark skin" might be a useful way of achieving that.

My glider has "turbulator tape" about 2/3rds of the way back along the underside of the wing to trip the laminar flow back into turbulent flow before it meets the trailing edge of the wing, as separating the flow here is more efficient. There must be places on the glider where it's impossible to maintain laminar flow with a smooth surface fuinish but where that would be advantageous for performance. Parts of the fuselage, for example. Here "shark skin" might be useful.

[Doctor Gollum]

Some interesting points here...

https://www.airliners.net/forum/viewtopic.php?t=765135

I had previously been told that the dimples aft of the trailing edge on the 757 was for airflow purposes.

A couple of interesting links too

[Gaffers]

I agree with the glider, there are places where the shark skin would be very useful but I would think that on the underside of the wing it would be counter-productive.  But then I am armed with a little knowledge in this area and I am far from being an expert.

Have you seen the ships where they push air bubbles under the hull to separate it from the water resulting in significant reductions in fuel consumption.

If I hadn't worked in IT and Cyber I think I would have worked in engineering somewhere.  Fascinating stuff!

[Kevin Wood]

I can imagine that's a big advantage for ships because water is such a dense medium, and drag is therefore so large that anything you can do to escape it is worthwhile - such as a hydrofoil where you induce quite a lot of drag to lift the hull off the water, but presumably the reduction in parasitic drag makes it very much worthwhile.

[STEMO]

I can imagine that's a big advantage for ships because water is such a dense medium, and drag is therefore so large that anything you can do to escape it is worthwhile - such as a hydrofoil where you induce quite a lot of drag to lift the hull off the water, but presumably the reduction in parasitic drag makes it very much worthwhile.

Ooo....a conversation about drag. 

[Doctor Gollum]

I agree with the glider, there are places where the shark skin would be very useful but I would think that on the underside of the wing it would be counter-productive.  But then I am armed with a little knowledge in this area and I am far from being an expert.

Have you seen the ships where they push air bubbles under the hull to separate it from the water resulting in significant reductions in fuel consumption.

If I hadn't worked in IT and Cyber I think I would have worked in engineering somewhere.  Fascinating stuff!

That said, the application being looked at in the link appears to be military, and fast jets aren't known for their ability to glide... Lift not being a primary consideration.