Hello, where to find information if already discussed.

[unodos96]

Hello, my name is unodos and I have come upon the ecomodder forum from the intersection of aerodynamic efficiency for fuel efficiency and performance based aerodynamics. ( Downforce, drag reduction, etc)

If this type of topic has been discussed please let me know where.

Possibly silly question, not going to be surprised to get clowned on BUT

My question in short form: Could I "tube" airflow from an area of high pressure, say from the front bumper to the rear and it be a "net positive" in drag reduction?

Longform: My car has 2 medium sized holes in the bumper which can technically be sealed up I have often wondered about utilizing this access point. The bumper, this being a FWD car, has preformed ventilation holes at the rear in order to, i assume, release high pressure air build up. Could I create an an air scoop/capture point and tube the air from the front of the bumper to the rear of the vehicle to reduce the low pressure zone that will form in this area.

I realize that there are probably much better ways to do this such as a diffuser, long (boat?) tail, etc but the space is there and it would be a bit less fabrication than those options.

Vehicle for reference: Volvo c30.

Air capture point: The headlight washer cap/containment area. For various reasons mine have broken off and I removed the washer nozzles.

Air release/disposal point: half of the bumper ventilation grills on the left and right of the rear lower bumper section. Image is dark but visible.

Rough idea would be to have no or minimal "scoop" aspect to the capture as not to disturb airflow over the headlights and front of the car. I am hoping that the high pressure formed by the air hitting the headlight and the slight downward angle of this section of the bumper would be enough to A. push air into the "tube" and B. the low pressure of the bumper area would be enough to "suck" the air through.

Little to no scoop is necessary as normally that area would have a very simple and small "cover" as in seen in the front image. A more "traditional" capture spot may be the lower foglight areas on the front but I will consider that if "tubing" air from the front to the rear is viable on its own in theory.

Thank you,
Unodos

[freebeard]

Aerodynamic drag comes in two forms -- Form drag and skin friction. Successful internal ducts are short, with a large cross section.

You could test your proposal by lashing your 'tube' to the outside of the car and placing a [Dwyer] differential manometer inside the openings front and rear and see how much flow you actually get.

You'd want to bell-mouth the front to resist vena contracta.

Do you have a route through the interior that isn't twisted and kinked?

I like the C30 -- lots of plan taper to the cabin.

[freebeard]

I guess I should answer the actual question.

Hello, where to find information if already discussed.

In the upper left you have the Search function. Click the Advanced button to limit search by forum, date, etc.

[Piwoslaw]

Hi Unodos,

Welcome to Ecomodder

Originally Posted by unodos96

Possibly silly question, not going to be surprised to get clowned on BUT

No, here you will not get clowned on for asking relevant questions, nor for tossing up ideas. If they were already discussed, you will either get an answer or a link pointing to the thread.
Even if you come to EM with snake oil or other charlatan-esque wonders, then we first ask for hard data, as we are open to new ideas. Only then we will try to explain why your proposal may not perform as advertised.
Only if you turn out to be less open than we are, and do not provide hard data nor listen to explanations, you might end up being the newest clown in the Unicorn Corral.

Regarding channeling air from the front to back, as Freebeard mentioned this seems to work when the distance is short and the cross-section large. In this form you can already find some examples in productions cars.
The longer the "tunnel", the more bends and kinks in it, the smaller its cross-section, and/or less circular it is, then the more internal drag it will have. At some point it will hardly be moving air and its benefits will be outweighed by the system's weight, cost or complexity.

Unless you can bore a large hole down the middle of your car, you will be better off with blocking those small holes and pushing the air to the side or top of the car, where the airflow is (hopefully) already smooth.

[freebeard]

The lower foglight areas could be useful. A short converging duct that transitions to a tall rectangle at the front of the wheelwell and you'd have air curtains.

[freebeard]

Here's an example that Cd posted in another thread: