Dielectric-barrier discharge (DBD) for drag reduction

[Piotrsko]

Reynolds number is mostly a speed where flows change. They were concerned with abrupt stalls on laminar flow airfoils and when the airfoil went laminar low drag. Nothing magical except the transition from turbulent to laminar and the equipment avaliable back then couldn't determine the point of the transition. Could be new stuff with computer analytics, dont care unless the surface is attempting to operate in That surface speed. Isn't useful for R/C gliders subsonic. I don't understand the mindless fixation on the transition point. Your either turbulent or not. The amateur definitely cant measure it

[Logic]

Originally Posted by freebeard

https://en.wikipedia.org/wiki/No-slip_condition


IMHO opinion (I don't have the time to read your links ) the plasma creates a virtual surface with a non-zero velocity for the bulk flow to adhere to.

Quite so. And more 'Down-Wind' with this new process.



For a start I imagine implementing it around the bottom right blue corner in this pic:


Then see here:

https://www.youtube.com/watch?v=yftKjkZHirc

Now instead of wires; what if your 'wires' were instead the trailing edge of the cooling fins of your cars radiator..?

I NB that modern car radiators are already electrically insulated from the rest of the vehicle to stop galvanic corrosion, so applying eg: -20 000 volts to them shouldn't be difficult.
(galvanic..?)

I'm not thinking of replacing the radiator fan;
I'm thinking about how much more efficient a radiator (or heatsink) gets if it doesn't have a boundary layer insulating it?
How much smaller could it be..?
(I imagine 'losing' heat exited electrons may have an effect on its own..? and is said to improve ionic thrust)

If so designed; there's no reason you couldn't also put eg: + 20 000 volt thin wires in front of a radiator's rounded cooling tubes if they stuck out further than the fins did.

[Piotrsko]

Well to get a heat sink that works as well as a radiator, you need the surface area of that radiator. It's a 3d radiator. You gain efficiency with higher coolant temps, higher pressure, slower speed of the cooling fluid, more air flow, maybe some other variables that would alter the delta involved.
You ARE sinking what ever btu you are burning generating horsepower, throughout the engine bay. Some leaves easily through the exhaust sysyem but that has losses also.

Somebody was once goofing with a Peltier exhaust system. Did work, but ROI was minimal

Nasa has an interest for their stealth aircraft since its a huge issue with targeting the aircraft you might not have the clearance to ask.

[Logic]

Originally Posted by Piotrsko

Well to get a heat sink that works as well as a radiator, you need the surface area of that radiator. It's a 3d radiator. You gain efficiency with higher coolant temps, higher pressure, slower speed of the cooling fluid, more air flow, maybe some other variables that would alter the delta involved.
You ARE sinking what ever btu you are burning generating horsepower, throughout the engine bay. Some leaves easily through the exhaust sysyem but that has losses also.

Oh I wasn't thinking of cars when I said heatsinks. More computers and such where silence beats efficiency.

The HS would have to be ground so as not to disturb the electrons in the nm wide silicone paths.
Then where would you put your thin wires to cut boundary layer as close to heat source as possible?

Also Ozone is an issue if you're going to be breathing the air.
IIRC you need a good finish on the rounded, low electron density surface under careful (to low) voltage control to avoid making it.

[blueoctagon]

Interesting tech but wonder about the power requirements.

[Logic]

Originally Posted by blueoctagon

Interesting tech but wonder about the power requirements.

This ionic wind occurs at voltages below those at which a plasma spark occurs and amps are very low.
As power in Watts = Volts X Amps; the amount of power taken is small.

eg: 20 000 volts X 0.0001 amps = 2 Watts.

Also:
I seems that the best way to power these is with a resonant circuit.
I'm heading out of my depth here but as I understand it a resonant circuit is way more efficient than circuits that aren't.
It's how (FM, AM etc) radio towers are able to work effectively and is used in a good many electrical/electronic applications.

[Logic]

I NB that, as suspected; ionic thrust/wind efficiency seems to increase as the initial airspeed over the surface increases:
"...Theoretically, at 1,080 km/h...it will reach 50% efficiency...."
https://aertecsolutions.com/en/2019/10/21/ionic-wind/

That makes a DBD system interesting as an induction enhancer.
ie: The engine intake system may well be made to have a lower pressure drop by a DBD system arranged on tube walls.
There may even be a very mild turo effect!?

Most interesting is that it would do Double Duty:
These things produce Ozone, which enhances combustion efficiency.

[Logic]

Originally Posted by Logic

That makes a DBD system interesting as an induction enhancer..

https://www.youtube.com/watch?v=rrqBugPPaNo

[freebeard]

It's a shame them didn't give the results from the hot wire anemometer.

[Logic]

Originally Posted by freebeard

It's a shame them didn't give the results from the hot wire anemometer.

Ye; I cant find the paper.

But he does say in the comments:
"Here's the range of the variables.
Voltage - 7.4 kV - 12.8 kV
Frequency - 20 kHz - 90 kHz
Current - 0 - 0.6 mA.."

That's 7.68 Watts.
Not much at all and way less than you lose to wind resistance IMHO..?

"...Compared voltage magnitudes & frequencies with flow velocities & observed maximum airflow of 9000 litres / hr ..."
https://www.linkedin.com/in/deveshdatwani

That's 2.5 l/s.
Not much, but I NB that the efficiency of these things increases dramatically with the initial air
At the airspeeds in an intake tract I'm guessing about 50% efficient.

This is what the intake from the air filter box into the manifold, or from manifold into intake track, should look like:

https://performancebyie.com/blogs/ie...ight-bellmouth

There it's easy to see where one would want to start putting DBD.

So you would get more flow along the intake walls AND there would be already be some momentum in the desired direction when the intake valve opened.
Something a turbo doesn't do...

But most importantly the DBD would ALSO be producing ionized air and Ozone which, at the right doses, does very good things for combustion if you read the studies.
The system would do double duty..!

Also O3 is more compact, so more Oxygen in the cylinder.