2003-GA Sidepod gills..

[Alex M3]

I'm curious about this because it relates directly to a discussion i've been having with BMW enthusiasts regarding vent designs. The 2003-GA, as you all know, had the gills aft of the radiator on the sidepod to obviously assist in ventilation.

Now, the physics department head at my school told me, or at least as i understood him, that the vacuum/exhausting effect of the louvred gills is only substantial is the velocity of airflow BEHIND them is relatively high. In other words, if the air behind the gills was stagnant then the louvred design wouldn't have much advantage over a simple hole/cutout.

I may have misunderstoof him, but is that correct logic?

[Monstrobolaxa]

Well.....after thinking a little about your post....well....to me if you had a normal hole in the body work of the car....air hot air would exit from this hole...due to the diference in pressure from the outside and the inside of the car....but...the air exiting would be in a turbulente regime.

With the gills the air is more or less laminar.......on of the things behind the conception of the F1 car is the reduction of drag.....and you have 2 kinds of drag....drag produces by the the shape of the "body" and drag created by pressure diference.....so the best way to reduce drag is to have the most laminar flow as possible.....in Ferrari's case they came up with a solution that helped in eliminating hot air and at the same time didn't create drag cause of the laminar flow exit......the fine if you pay attention tend to send the air in one direction.....if they weren't there....you would have a hole...an if it has the same size....air would exit in an aleatory way....increasing the drag.

[Guest]

Alex,

Sorry, but no laminar theory here. It once again comes back to Bernoulli. If there was a stagnant region at the position where the louvres exit it would automatically mean that a high pressure region would exist there. As the flow sees a positive pressure gradient already through the radiator duct an additional high pressure behind the radiator would make the flow even less likely to enter the duct. Too high a pressure gradient and the flow will separate (which results in drag increases). If however air would rush over the bodywork there at high velocity, a low pressure region would exist and hence this would help air get through the radiator. The little wing in the picture will surely help to create such fast moving air in that region.

[Alex M3]

Ok, i see what you're saying Guest, but is my presumption correct? That unless you have high velocity air behind the opening the gills are not essetial. The reason I think this may be true is that's exactly how the Ferrari 360 Stradale Challenge engine bay cover is vented. With simple holes. See below.

Now, the 2003-GA sidepod would have high velocity air in that region, thus the gills WOULD assist in extraction. Am i crazy or is that correct.


EDIT: replaced image with a resized one.. so that it fits on each screen without scrolling

[Steven]

hehe... you can be correct and crazy at the same time though

Anyway, you're correct. A high speed airflow in that area pulls air out of the inside of the sidepod, just like on the 360. Air flowing over the outlets tends to speed up slower air around, and vice versa.
So the outlet air is kind of sucked out. The effect is more or less like walking on the street, and when a truck has passed, you feel that your body wants to go with the flow (there are some nuances in the way this is created, opposite to here, but I just mean the effects are more or less the same.

[Alex M3]

A high speed airflow in that area pulls air out of the inside of the sidepod, just like on the 360. Air flowing over the outlets tends to speed up slower air around, and vice versa.
So the outlet air is kind of sucked out.

Right, but i'm talking about the air behind/underneath the bodywork.

Scarbs? Any thoughts?