Dielectric-barrier discharge (DBD) for drag reduction

[Logic]

DBD for attached flow on a car's rear:

See an orange line: that is a plasma actuator one would place at the beginning of a shallow boat tail.
One too shallow or short to keep flow attached under normal circumstances.

NB the power required for this stuff from the previous post.

https://www.youtube.com/watch?v=arG3g_xaKvU

[Logic]

Hmmm... that looks like to open end of a Bell Mouth or Velocity stack:

https://www.youtube.com/watch?v=mnCmvxt2jn8

[aerohead]

Originally Posted by Logic

NB how the air is NOT staying laminar over this stalled wing at a high angle of attack.
Then tell me how it's simply NOT going to keep flow attached on a short/er boat tail because I don't have Reynolds' number!

Lets NB that an electron traveling at around 175 000km/h (IIRC) does not stop until it's inside the 2nd surface.
Any air molecule that may have been ionized by said electrons may well be traveling a lot slower, but also does not stop until IT is the molecule on the opposite charged surface.
ie: Airspeed is of little importance here and Boundary Layer is no longer part of the equation!

For anyone else who doesn't give a buck afout Renaults or his nucking fumber after seeing that,
See B here for how you do DBD:

in this paper here:
https://www.nature.com/articles/s41598-019-42284-w

Here are all the high voltage doodats you might require:
https://ioninjection.ponderworthy.com/articles/parts

1) Pick a useful 'size' for your wing.
2) From it's 'length', reverse-engineer it's required velocity in standard air, based upon the given stated Rn.
3) Then explain to the global community how they could derive any possible benefit in the 'real world ' from the 'so-called' technology, when applied to automobiles operating at common posted speed limits.
( the big clue is, the difference between a laminar, and turbulent boundary layer )

[Logic]

Aerodynamic Drag Reduction and Optimization of MIRA Model Based on Plasma Actuator
"...Specifically, drag reduction is better when the actuation is applied at four positions simultaneously. The maximum drag reduction coefficient of the car is reduced by 13.17%..."

... This suggests that the plasma jet can obviously inhibit the flow separation in the tail of the vehicle and strengthen the aerodynamic characteristics of the vehicle


https://www.mdpi.com/2076-0825/9/3/64


Dielectric barrier discharge actuator for vehicle drag reduction at highway speeds
We propose and demonstrate reduction of aerodynamic drag for a realistic geometry
at highway speeds ... the measured drag reduced by over 14% at 26.8 m/s (60 mph) and over 10% at 31.3 m/s (70 mph) opening up realistic possibility of reasonable energy savings for full scale ground vehicles.
In addition, the power consumption data and drag reduction effectiveness for different input signals are also presented...

...Additionally, we also showed that the actuator can save 2.7 % total
drag average per watt power consumed with AM input signal and save 2.1% total drag average per watt with continuous input signal..."
https://www.researchgate.net/publica...highway_speeds

[freebeard]

The obtuse corners at the roof and rear fender are most likely to generate a vortex (mismatched airspeeds on the top and sides). That's where the help is needed most.

In addition, the power consumption data and drag reduction effectiveness for different input signals are also presented...

Are they over unity?

[Logic]

Originally Posted by freebeard

The obtuse corners at the roof and rear fender are most likely to generate a vortex (mismatched airspeeds on the top and sides). That's where the help is needed most.



Are they over unity?

I would say yes and no:
I THINK the power required to persuade some air to change the direction it was headed in some and stay laminar is less than the power lost to drag/turbulent flow.
That's why there's so much research in this area.

I NB that the studies seem to be using AC DBD rather than pulsed, unidirectional DC.
No self tuning resonant circuitry is mentioned so think the numbers could actually be better.

"AI Overview [Resonant Circuit]

A tuned resonant circuit, also known as a parallel resonant circuit or tank circuit, can maximize power by efficiently transferring energy between its inductor and capacitor [the DBD in this case]:

Resonance
When a tuned circuit operates at its resonant frequency, the current is minimized, the impedance is maximized, and the voltage is maximized. This allows the circuit to absorb and store energy from an external source very efficiently.

Energy transfer
The tuned circuit's action is similar to a pendulum swinging back and forth, or water sloshing back and forth in a tank. The energy oscillates back and forth between the capacitor and the inductor until internal resistance causes the oscillations to die out.

Applications
Tuned resonant circuits are used in many fields, including wireless communication, filtering, and sensor technology. They are also commonly used in communications equipment to select a specific range of frequencies"