Plasma drag reduction

[freebeard]

For it to be magnetohydrodynamics, we'd be introducing an electric potential, to accelerate the air itself to create jet thrust. I can't imagine that the mechanical efficiency could exceed that of an electric traction motor. It's a second law of thermodynamics fail.

That's exactly how plasma actuators do.

The efficiency (and the dust-collecting aspect) is made available for A-B testing and verification with the Subaru part (plus a signal generator).

[aerohead]

Originally Posted by freebeard

That's exactly how plasma actuators do.

The efficiency (and the dust-collecting aspect) is made available for A-B testing and verification with the Subaru part (plus a signal generator).

I'll leave the financing, fabrication,testing, and verification, under controlled laboratory conditions, plus peer-review, to anyone interested. That would not be me.
Is a sure-thing, Cd 0.10, with low-tech, not good enough?

[freebeard]

Why not both? I suspect there's opportunity to finesse the details, as with vortex generators.

In other news, I added a wickerbill to the corner of my Airstream and now the prevailing NW wind that used to blow the door open blows it shut. Aerodynamics works!

[aerohead]

Originally Posted by freebeard

Why not both? I suspect there's opportunity to finesse the details, as with vortex generators.

In other news, I added a wickerbill to the corner of my Airstream and now the prevailing NW wind that used to blow the door open blows it shut. Aerodynamics works!

Snake oil and unicorn farts.
The first video credits flow reattachment behind a reverse step, which would happen without any enhancement anyway. A tonneau cover does this. A box-cavity does this.
Then they make the leap that wake separation would be significantly constrained, when there exists zero surface onto which the flow would reattach to.
All the following videos deal with 2-dimensional flow, not germane to the real world.
No one addresses the enormous longitudinal vortices and vortex drag which would be created if the flow should succeed in following what their cartoon of the world implies.
And of course, in their world, conservation of energy isn't required, the Second-Law of thermodynamics doesn't exist, and all the real horsepower necessary to alter the wake flow magically disappears, when ' plasma' is doing the work, plus the drag of the inviscid flow immediately outside the modified wake is no longer is required to exist, because one simply whisks it away in the cartoon.
Obviously, only the power of a wrist watch battery should be sufficient to power such a device for a few hundred thousand miles. Why not? It's a cartoon! Why bring up the topic?

[freebeard]

According to Google, this is the numero uno 'plasma' thread, so here's this:

Defense Updates: U.S 6th GENERATION FIGHTER IS DEVELOPED IN A YEAR & HAS ALREADY FLOWN! IT HAS “BROKEN RECORDS” TOO !

It's not covered directly by that video, but consider it alongside this:

thedrive.com/the-war-zone/: Blasting The Air In Front Of Hypersonic Vehicles With Lasers Could Unlock Unprecedented Speeds



Figure V-24: Ooh-wee-oooh....

[Piotrsko]

That laser thingee is a bit far fetched, recall the laser they hung on a commercial style airplane which was mostly power supply for payload

Even if you could get 100% efficiency, you'd still need a bunch of k-watt generation sucking up fuel.

[aerohead]

Originally Posted by Stubby79

Soo...we're talking about electromagnetic golf ball dimples?

Dimples would be a redundancy, as there already exists a supercritical Reynolds number and complete turbulent boundary layer protecting against flow separation.

[aerohead]

Originally Posted by kach22i

I think the force field analogy fits best, but it's micro eddies or small vortexes of disturbed air forming a protective film or barrier which allows passing air to pass more easily.

Golf ball dimples, shark skin etc.............all depend on the passing fluid (air/water) to initialize the event.

Dimples are passive, this thing is active.

1) As it stands, it's the dead air in the lowest strata of the turbulent boundary adjacent to the trucks body surface boundary which is protecting the attached flow.
2) The truck is already fully immersed in 3-D micro eddies transporting momentum from the outer flow all the way to the boundary, pinning the air.
3) I'm unsure as the the premise of how the plasma actuators would improve the existing situation.

[aerohead]

Originally Posted by freebeard

https://en.wikipedia.org/wiki/Pitot_tube



I've been thinking that the drip rail down the front of the doors on a VW bus is well within the frontal area. A serrated Gurney flap there would be exposed on the leeward side and could have a similar effect if it were sized appropriately — maybe 1/2" to 1 1/2" serrations? Worth a Photoshop?

It would have to 'travel', fore and aft, around on the body, as the apparent wind spectra could be constantly changing orientation.

[aerohead]

Originally Posted by freebeard

2nd paragraph is unnecessary.

Plasma actuators make the air move faster, locally; unless I'm too dumb to comprehend anything.

If so, then this higher local velocity will induce a lower local pressure, with surrounding air seeking this local low, from any direction, attempting equilibrium.
What is it about this situation that would be of benefit?