Radiator hood vent?? Aero, cooling, WAI, all in one??

[jeff88]

Originally Posted by Vman455

It's making me want to cut up my hood and put a small gaping hole in it.

As long as your 'small' hole is 15% bigger than your radiator opening...
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Aerohead, that car looks aeroynamically sound, but I don't see any extractors (or holes of any kind). Can you elaborate in layman's what they are doing?

[aerohead]

Originally Posted by jeff88

As long as your 'small' hole is 15% bigger than your radiator opening...
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Aerohead, that car looks aeroynamically sound, but I don't see any extractors (or holes of any kind). Can you elaborate in layman's what they are doing?

If you look directly above the front wheel,near where the windshield edge would be,you'll barely make out a slot which is oriented with the color dye solution.
I believe that there are corresponding slots below as well.
Morelli divided the cooling air coming out of the engine bay into 4-different streams and experimented with duct size and geometry such that the air escaping out these slots blended perfectly with the surrounding flow field.
An isobaric/velocity contour map was created by pressure tap and velocity pressure measurements (you see this today in color CFD mapping),and working with Bernouli's Theorem,arrived at duct sizes which provide the air volume at a matched velocity,given the pressure environment its flowing into.
This cannot be modeled analytically yet and must be done by trial and error in the tunnel.(very expensive!)
If you get it wrong:
*air can flow into the exits
*jets can be formed which trigger shear-induced vorticity,eddies,turbulence
*Transverse-vectored jets can contaminate the boundary layer,trigger separation,along with the formation of form additional vorticity.
My opinion is that 'nailing' this sort of thing is completely outside the scope of what individuals can pull off without major money.
*air can stall within the duct

[chillsworld]

Originally Posted by aerohead

If you look directly above the front wheel,near where the windshield edge would be,you'll barely make out a slot which is oriented with the color dye solution.
I believe that there are corresponding slots below as well.
Morelli divided the cooling air coming out of the engine bay into 4-different streams and experimented with duct size and geometry such that the air escaping out these slots blended perfectly with the surrounding flow field.
An isobaric/velocity contour map was created by pressure tap and velocity pressure measurements (you see this today in color CFD mapping),and working with Bernouli's Theorem,arrived at duct sizes which provide the air volume at a matched velocity,given the pressure environment its flowing into.
This cannot be modeled analytically yet and must be done by trial and error in the tunnel.(very expensive!)
If you get it wrong:
*air can flow into the exits
*jets can be formed which trigger shear-induced vorticity,eddies,turbulence
*Transverse-vectored jets can contaminate the boundary layer,trigger separation,along with the formation of form additional vorticity.
My opinion is that 'nailing' this sort of thing is completely outside the scope of what individuals can pull off without major money.
*air can stall within the duct

Did he "tune" the vehicles aerodynamics to a particular speed or range of speeds? I've been reading about ducting inlet/outlet size and it's impact on matching exhaust of the duct to external air speeds... So far everything I have read about it says that you would only be matching in certain situations. For example, when I posted earlier from the thread about designing duct work, it pertained to the student race cars that don't see high speeds. The consensus with them, was that exit speeds didn't matter because they didn't obtain speeds where a difference is air speeds would be noticed. I'm on my phone right now, I'll try to post something more substantial tomorrow from my computer.... But I was just wondering if you knew off the top of your head? I mean that would be a lot of variables that would need to work perfect to even match a single speed, much less all speeds??

-C

[aerohead]

Originally Posted by chillsworld

Did he "tune" the vehicles aerodynamics to a particular speed or range of speeds? I've been reading about ducting inlet/outlet size and it's impact on matching exhaust of the duct to external air speeds... So far everything I have read about it says that you would only be matching in certain situations. For example, when I posted earlier from the thread about designing duct work, it pertained to the student race cars that don't see high speeds. The consensus with them, was that exit speeds didn't matter because they didn't obtain speeds where a difference is air speeds would be noticed. I'm on my phone right now, I'll try to post something more substantial tomorrow from my computer.... But I was just wondering if you knew off the top of your head? I mean that would be a lot of variables that would need to work perfect to even match a single speed, much less all speeds??

-C

Above 20-mph,the coefficients of drag for all the components of the car would be fixed,up to around 250-mph,when compressibility effects started to show up,so all their individual behaviors would be constant.
As long as you tuned in a turbulent boundary layer,everything would track in the same proportions.

[chillsworld]

Originally Posted by aerohead

Above 20-mph,the coefficients of drag for all the components of the car would be fixed,up to around 250-mph,when compressibility effects started to show up,so all their individual behaviors would be constant.
As long as you tuned in a turbulent boundary layer,everything would track in the same proportions.

That makes perfect sense. Their cars are run on tracks where they rarely get over 20mph (from what I gathered)... So their comments would make sense given that context from you

[freebeard]

The only thig I can see that might complicate things would be intermttent cooling fans that don't track with vehicle velocity.

[aerohead]

Originally Posted by freebeard

The only thig I can see that might complicate things would be intermttent cooling fans that don't track with vehicle velocity.

Yeah,we're kinda stuck with them until material technology allows an adiabatic engine with zero cooling.
For continuous highway driving we don't need a fan at all.CAR and DRIVER illustrated that one back in '74.
I drove the Dodge 100-mile round trip without one,running the heater on high for auxiliary cooling on surface streets 'til I got home.

[whatmaycome14]

So, here's a question. I'm actually at the point where I'm ready to cut the hood, however, the upper radiator hose is significantly in the way. Does it matter if this is 1) off center and not symmetrical, or 2) only half (or less) the width of the radiator?

[freebeard]

So... Bring us up to date since 08-16-2014, 06:44 AM.

MMY? [make, model, year]

[whatmaycome14]

Originally Posted by freebeard

So... Bring us up to date since 08-16-2014, 06:44 AM.

MMY? [make, model, year]

If you're asking about mine, its a 2003 Honda Civic (see in my sig)