Sharks gills on sidepods

[eweturn]

I am just wondering about the shark gills (kews I think they are called) on the sidepods that seem to be becoming required more and more. From what I can gather, this is due to the cooling requirements of the engine, in addition to the chimneys on the top of the sidepods.

Can anyone explain why they would not try and expel this air into the diffuser area in the fashion that they use to with the exhaust gases? The benefit that I can see if that the air would be less dense, thus it could have the potential to contribute to the production of downforce of the diffuser. Also, due to there being a low pressure region under the car, this would promote airflow through the sidepod. Or better still, maybe a smaller outlet for the same airflow?

I concede that there would be a reduction in efficency due to having an outlet in the diffuser. However, would it be any worst than the reduce efficiency from disturbance around the rear wing and wheel?

Now on a different tack, does anyone else think that there is potential downforce being wasted by not utilising the exhaust gas from the engine. For example, some jet aircraft use a system called blown flap that uses airflow from the engine to re-energise the boundary layer (http://aerodyn.org/HighLift/powered.html). I’m not sure how to do it though. Maybe lower the rear wing (however it work better closer to the free stream) or a winglet behind the exhaust (may interfere with the airflow around the rear wing). I guess that is why nothing has been done.

The same principle could be used for the shark gills. If they were closer to the winglet in front of the rear wings with the outlet on the underside. The reduced air density due to the expelled heated air could contribute to downforce.

With respect to radiator cooling, has any one heard of the teams using dry ice? Not sure how, maybe in tubes inside the radiator or around a reservoir somewhere?

[Monstrobolaxa]

Well about the diffuser and the exhaust gases....well the diffuser works by creating a lower pressure system then under the car, creating a suction effect, if you increase the mass of gas in the diffuser, even if the gas you introduce is less dense, the pressure would rise slightly reducing this suction effect.

The other disadvantage is that the amount os gases expelled by the exhausts is not constant so you would have diferent amounts of downforce for diferentes amouts of exhausts....which will make the car slightly more "nervous".

[marcush.]

The point is:
Every hole or leak into the underfloor reduces downforce considerably.
So there is no point having waste heatair stream in the diffusser,as it essentially makes the whole system inoperative in terms of creating downforce.
The vents and gills on top of the car in contrast add drag of course but they can actually increase downforce created,so the car is just a tad less efficient. so teams knock of some wing to counter that.
Blowing the diffusser,is a ,well two folded sword:In very slow corners ,perhaps Casino or pascasse in Montcarlo...you are actually very slow and flooring the throttle ther will create quite a bit downforce and you might have more traction that way without having to move very fast,
the high revving engine blowing enough air thru the diffusser to create suction.
The faster the car goes the less you want an additional source of air expanding into the diffuser,even though the gases are travelling at a considerable speed relative to the car and more so to the ground,the energizing effect will surely have a disturbing effect on balance.
Better is blowing the top of the diffuser ,a concept invented by alan
mertens of Galmer for his award winning Indycar
the exhaust tip is effectively the trailing edge of the diffusser,blowing
exactly inthe direction of its ramp elongating the diffusser somewhat,
or acting like a gurney,without adding drag...but maybe it also unbalances the underflow aero too much as in F1 this has been used by williams (if I remember correctly) but has been abandoned ...
Aero is good as long it is fluctuates not too much with the car heaving,pitching and rolling with brakes applied or when you go hard on the throttle,or going of it.
If the aero change compromises the balance of the car in a sudden way
the thing becomes a dog to control.

[dumrick]

I read somewhere that the short exhaust are justified by requests of the engine guys, not by aerodynamics.
For sure, the trade-off between loss of downforce and increase of power favour this layout, and the exhausts can no longer reach the diffuser, combined with the disavantage in pitch and throttle sensitivity of the older solution. Nevertheless, Newey tried to come back to this solution in the MP4-18, if I'm right.

About taking advantage of the energy of the exhaust, one must remember that the energy in the flow (speed+temperature) is far higher in a jet engine than in an internal combustion one, as well as the mass of air used. So, maybe in an F1, there isn't that much energy to take advantage of.

[marcush.]

one would be surprised of the air masses channeled thru an engine at the rpm levels in F1 ...
Why should there be a problem to put the exhaust in the tunnels?they effectively begin at the front of the rear tyres ,exactly where the exhausts emerge thru the top of the bodywork ....
A very big factor has to be the waste heat of the exhaust gases not affecting the gearbox and the diffuser itself ...

[scarbs]

The shark grills are simply a duct to vent hot air form the sidepods, the are sited so far forwards as the heat can escape early allowing for a smaller sidepod width between the rear wheels, which is the area most flow used to exit from the sidepods. Wide sidepods between the rear wheels create a lot of drag, Ferraris recent emphasis on slimming them prompted mnay more forward placed outlet ducts. The have louvers to collect and calm the messy flow inside the sidepod.

Exhaust blown diffusers have been used for years Renault adopted in 1983, F1 teams found them too sensitive as the DF created by the exhaust varied with engine loading through a corner. The exhausts got moved further up the diffuser to reduce the sensitivity until routing the pipes through the suspension created an aero blockage, negating the initial benefits. Plus the heat absorption problems for the carbon suspension in close proximity to the pipes.
Added with the requirement for shorter pipe lengths demanded by the engine suppliers, the teams put the exhausts through the top of the sidepods, they used blow under the lower wing beam, but now appear to blow over the beam. Instead the exhaust gas velocity is used to pull air through the sidepods for improved cooling.

No F1 teams does a lot of tunnel work with heated flows, they are hard to create and hard to get accurate repeatable results that correlate to track testing. Even the representation of fast exhaust gasses are not generally part of the tunnel process.