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Porous skins to maintain laminar flow
Posted: 18 Nov 2009, 16:17
by meves
I was looking at patents (as you do) as wondered had this been tried/or would it work in F1? It has been designed for engine aircraft covers (a nacelle)
A laminar flow control arrangement for use in a nacelle for an aircraft turbine engine. The nacelle has a microporous outer skin in the area where air flow over the skin is to be maintained in laminar flow. A honeycomb core is bonded to the inner surface of the nacelle skin. A perforated back skin is bonded to the inner surface of the core. Several closely spaced circumferential flutes open to the back skin are fastened to the back skin. At least one collector duct is connected to the flutes and a suction pump. In operation, the suction pump pulls air through the ducts and flutes, causing air to be sucked inwardly through the microporous skin thereby maintaining laminar, rather than turbulent, flow over a large part of the nacelle during aircraft take-off and cruise operation. In addition, a chamber is preferably provided in communication with any gaps in the nacelle skin in the area where laminar flow is desired. Air is sucked through said gap and adjacent chamber to avoid disruption of laminar flow by the gap. A significant reduction in drag results for a nacelle incorporating the novel arrangement of the present invention.
http://www.freepatentsonline.com/5297765.html
Re: Porous skins to maintain laminar flow
Posted: 19 Nov 2009, 01:57
by flynfrog
Aircraft jet engines use simaler system on the inlets to reduce noise check it out next time you fly if you can see in the inlet you will see a bunch of tiny holes.
Re: Porous skins to maintain laminar flow
Posted: 19 Nov 2009, 07:54
by Fil
some of the bikes in 125 & 250cc used a similar principle i believe, but allowing airflow to utilise the holes.
Re: Porous skins to maintain laminar flow
Posted: 19 Nov 2009, 11:32
by meves
I was wondering if they can generate the same effect with tiny holes or a porous surface with microscopic holes to stay within the rules. Over areas like the sidepods could it be used to improve aero performance by maintaining flow better over highly sculpted sidepods or just by reducing drag especially at high speeds.
Re: Porous skins to maintain laminar flow
Posted: 19 Nov 2009, 14:28
by casper
I would think the perforated structure will fail the crash test.
Re: Porous skins to maintain laminar flow
Posted: 19 Nov 2009, 18:05
by BreezyRacer
Porous skins can erase downforce and lift tendencies of a shape. Very useful it's that's what you want to do .. They can be slots, holes, or screens.
Re: Porous skins to maintain laminar flow
Posted: 19 Nov 2009, 19:38
by kilcoo316
meves wrote:would it work in F1?
Nope.
No use in airflow with a turbulent freestream.
Re: Porous skins to maintain laminar flow
Posted: 23 Nov 2009, 17:06
by ubrben
Fil wrote:some of the bikes in 125 & 250cc used a similar principle i believe, but allowing airflow to utilise the holes.
Not the case - those holes are to reduce cross-wind sensitivity.
Ben
Re: Porous skins to maintain laminar flow
Posted: 23 Nov 2009, 20:32
by Ciro Pabón
casper wrote:I would think the perforated structure will fail the crash test.
On the contrary: perforated structures are more resistant. I know that idea goes against structural design, but anyone who has tried to rip a toilet paper through the tiny holes it has, knows that it breaks anywhere but through the holes...
Re: Porous skins to maintain laminar flow
Posted: 24 Nov 2009, 00:25
by flynfrog
remind me to send you some american toilet paper. We have solved those issues and its soft too.
Re: Porous skins to maintain laminar flow
Posted: 24 Nov 2009, 17:50
by ringo
the concept could be a nice way to reduce boundary layer thickness under the floor of an F1 car. It's against the rules but a pump could be place internally to suck on the porous floor.
Increased downforce with lower ride height can be achieved with thinner boundary layer.
Re: Porous skins to maintain laminar flow
Posted: 24 Nov 2009, 23:40
by Richard
casper wrote:I would think the perforated structure will fail the crash test.
Honeycomb structures are stronger per kg than solid. I can't see why that wouldn't extend to to a porous surface created with holes linked to the inner honeycomb.
Re: Porous skins to maintain laminar flow
Posted: 04 Dec 2009, 06:18
by riff_raff
meves,
There have been aircraft wings made with porous surfaces that allowed the boundary flows to be sucked away, thereby maintaining laminar flow over the entire airfoil at all times. The drawback was that the porous surface was very difficult to maintain and the vacuum system that bled off the boundary layer was very complex.
http://www.nasa.gov/centers/dryden/pdf/ ... H-2382.pdf
Other than that, it worked very well though.