Boundary layer suction?
 

What do you guys think about using Boundary Layer Suction to reduce drag?
BLS uses pump to literally suck the drag-creating boundary layer:
Boundary layer suction - Wikipedia, the free encyclopedia

What would be the optimal place(s) to place the inlet holes?
Remember that most cars have a huge angles when transitioning from grill to hood to windshield to roof.
So I think the inlet holes would be better placed in over the hood and the roof and in the bellypan. Maybe also on the doors or fenders.

The vacuum pump may be wired so it turns on at certain speeds reducing its power consumption during stop and go traffic.

One patent addressed its use in the underbody:
Patent US20080252099 - Boundary Layer Suction System For A Vehicle - Google Patents

skin drag is pretty small in our world, which is what this addresses.

Form drag is HUGE.

The problem you would solve with this would probably not be measurable.

And then you'd have to power the pump too as I don't think you could route "suction" from elsewhere to do the job.

What I recall reading a few years ago is that NASA thought it was a good way to reduce noise.

Some say those silent black helicopters circling overhead use this technology.

Old Thread, see post #8
Fan & Propeller shapes: Sickle and Curved
http://www.grc.nasa.gov/WWW/RT/RT200...ningham-f1.jpg

Ducted to the low pressure wake behind the vehicle? I don't know if the pressure difference is enough.

Seems like a pretty small gain for a lot of work, though. Do this after you have a full boat tail and a Volt style electric drive system with automatic P&G.

It's not about skin friction.

By sucking out the stationary boundary layer you get less flow separation thus less drag.
In practical terms you get lower drag equivalent to a more aerodynamic shape.

Beyond certain speed the power required to power the pump is overcompensated by the lower aero drag.

The drag coefficient is reduced by 20.25% using this strategy
Active Flow Control over the Car

The drag is CALCULATED/ESTIMATED to reduce drag that much... while increasing lift about the same amount? :confused: We don't want lift.

What speed is that and how much power does the pump require?

Take a look at Jim Hall's Chapperal cars of the 60's and later his Indy car program. The physics haven't changed.

suction
 

You might want to check in with the folks at Georgia Tech University.I believe they have on-going research with this technology.
The affects of blown and suctioned slots is a mature science now,but for MPGs they haven't conquered the cost factor.So far it's been a net loss energy wise,absorbing more energy than is saved.Like Coanda's airplanes.
The first research in this field was demonstrated by Ludvig Prandtl.He would be your starting point.

OAUGDP:

Aerodynamic Boundary Layer Control Using EHD Effects of a One Atmosphere Uniform

Saw this demonstrated a few years ago, pretty impressive. Not sure the energy required to generate the flow, but the small model I saw plugged into an outlet.

RE:
Electrohydrodynamics - Wikipedia, the free encyclopedia

I've heard of a woman in Ann Arbor, MI which may be using something similar to generate electricity from wind, but without using any moving parts.

Dang, I hate paying for things on the Internet. Guess I'll have to wait until this one becomes common knowledge.:cool:

I think in gross terms, most people fail to recognize the HUGE volumes of air involved in the automotive aerodynamic equation, conservatively speaking, the air within 15 feet around a typical car and 150 feet behind it, is seriously disrupted by the passing of a car. The math works out to approximately 150,000 cubic feet of air per second passing over the body. I find it difficult to believe that the minute amount of air at the boundary layer region is going to have much impact on this. Big picture thinking calls this one an impractical way of doing things...sort of like saying that if we could get a sparrows wings to beat fast enough, it could propel a Cessna.

But if you want to believe that the 1/2 inch layer of air around the car is all that matters in aerodynamics, feel free to keep deluding yourself, good luck, be certain to report back your results.

Also how well would this hold up the real world before the road dirt, dust, bugs, and other grunge flying past clog up most of the vacuum holes. The aircraft using this technology were flying 1000's of feet overhead where there are mimimal amounts of small debris in the airstream, not driving behind a semi kicking up a plume of dust behind it.

Schlicting
 

I looked through Hermann Schlicting's book,'Boundary Layer Theory'.He sites 46-researchers who've actively investigated blown/suctioned structures,from Prandtl's first paper in 1908,through 1976.
There are probably more but my German isn't very good.
Also,if you can snag a copy of the book Race Car Engineering by Paul Van Valkenburg (sp?),in the very back of the book he has smoke photos of a model Corvette,with,and without suction.It's remarkable..
In my seminars or mod data lists there's also a siting for a fellow by the name of Cornish III who was involved.
Alex Tremulis,writing in the early 1980s had presumed that by now,all cars would have active aerodynamics with Cds of 0.12 using suction slot technology.
Israel's solar-pond driven turbo-generator power production,married to a vehicle's exhaust system may be able to extract enough heat to power a pump.It would be a thermodynamic coup,moving closer towards an 'adiabatic' vehicle.

one more reference
 

I located my last reference.
Kawanishi Aircraft Corp. produced the Shin Meiwa PS-1 and US-1 amphibious aircraft which is a STOL design.It is powered by 4-General Electric gas turbine,turbo-prop engines,and there is a 5th gas turbine embedded within the upper fuselage behind the wings which furnishes compressed-air to the flaps,rudder,and elevator.
The propulsion engines are rated at 3,060 ehp each,there is no mention of the 'pump' engine.