@Grymnir (achtung: langer post!)
... nach weiter überlegung & recherche nach passendem bildmaterial
;) nun folgendes:
http://www.allmystery.de/themen/uh84125-64#id10722929
also die theorie ist mal banane!
weil:
da hab ich garnicht den coanda-auspuff in diese gedanken miteinbezogen. tststs ...
Grymnir schrieb:Man sah neben den Reifen, daß der Auspuff auf das Seitenblech des Heckflügels bläst. Ist das nicht verboten??
ich gehe davon mal aus, dass diese cam ein bild von "oben" gezeigt hat, und nicht von der seite. oder?
weil dann sehe es so aus, dass es auf den heckflügel zielt, aber es in wirklichkeit nicht tut
(näheres dazu auch am ende des posts)!
da war meine erste vermutung schon eher richtig (eigtl. ist sie es sogar
:D ), bis auf die tatsache, dass ich mich mit den begriffen vertan habe!
Corellian schrieb:dass man durch dieses "squirting" soviel wie möglich alles "unsaubere" vom diffusor fernhalten will ...
mit squirting meinte ich also den coanda-effekt, und mit unsauber das tire-squirting eben!!!
erspare mir jetzt weitere worte meinerseits, sondern überlasse dich (auch
@Fusselkater) diesem längeren text in englisch
:D :
"Although the FIA move was not delighted all teams, with some expressing reservations in a meeting of the FIA's Technical Working Group, the majority of outfits have welcomed the move - because it effectively removes a grey area of car development.
The FIA argued earlier this season, during an intended push to ban off-throttle blown diffusers which eventually had to be abandoned, that such extreme engine maps were a breach of the famous Article 3.15 of F1's Technical Regulations.
This was based on its view that there was an aerodynamic benefit from a moveable part (engine and throttle), plus it was being influenced by the movement of the driver through the throttle. Neither are allowed in the rules. This new hanges to the technical regulations have thrown things back into the melting pot and it remains to be seen who has done the best job of re-interpreting them. Change in exhaust exit pipe position, diameter and profile led to loss of rear-end downforce, sending aerodynamicists searching for fresh ways to regenerate it and rebalance their cars.
New positioning of the exhaust pipes exits and limitations are shown on picture below. Exits of the pipe can be positioned inside green box with exhaust tailpipe pointed upwards.
But this was not sufficient to eliminate exhaust-blown diffusers. Well, the first thing to note is that it is not possible to point the exhaust exit down at the diffuser in same way as before, this will not necessarily prevent the exhaust jet itself from blowing in that direction. When an exhaust jet exits into a cross-stream of fresh air, the exhaust jet bend with the air stream, effect called "Downwash".
...
If the exhaust exit is placed flush in the rearward face of sidepods sweeping downwards at a fairly steep angle, then the free stream airflow could deflect the exhaust jet downwards in direction of the diffuser. The degree to which the jet is deflected is determined by the ratio between the velocity of the jet and the velocity of the cross-stream flow. The smaller the ratio, the more the jet is deflected. This effect is well documented and often termed “jet in cross flow”.
After that, coanda effect (Coanda – The tendency of a gas or liquid coming out of a jet to travel close to the wall contour, even if the wall’s direction of curvature is away from the jet’s axis) will take over and "glue", now energized air stream (mixed with exhaust jet) to the bodywork. Of course, secret is to design this part of the bodywork and bodywork in front of the exhaust exit in the way to optimize this effect and give a proper and exact route for gasses to flow in diffuser direction. Effect of diffuser blowing is not as strong as before, but with clever design and optimization you can get few percent of download more. With this set up the exhaust plume is curved downwards by both the shape of the bodywork aft of the tailpipe (coanda) and by the airflow passing over the sidepod (downwash).
During 2012 pre-season testing, already few teams come with this new solution. Sauber Racing and McLaren found a way of shaping the sidepod and exhaust fairing to use these effects. They where able to consistently direct the exhaust jet at the gap between the diffuser and rear tire. McLaren’s exhaust\sidepod solution has proven to be the most widely adopted and has been termed a "Coanda" exhaust by the media. Even though it’s arguably an inaccurate term, as the downwash effect is probably greater than the Coanda effect in comparison to other sidepod shapes, such as Red Bull’s. They come first, and then Ferrari, Force India, Toro Rosso, Sauber and Caterham , followed by Williams and others. Lotus was the last team to follow the trend for the Coanda-effect exhaust system, introducing it from Friday in Korea GP on Kimi Raikkonen's car, providing exhaust-boosted airflow over the rear brake ducts and around and over the diffuser sides. Kimi continued to use it in qualifying and race, while team mate Romain Grosjean kept the old, central-blowing exhaust, which provides slightly more engine power. This leaves just Red Bull following the fully ramped sidepod design, and HRT remain with a simple periscope exhaust set up.
Diffuser has low pressure inside, this will draw in high pressure airflow from outside the diffuser reducing its downforce. Additionally, the tires wake sends an unwanted jet of airflow into the diffuser, known as ‘tire squirt’.
Unable to blow directly into the diffuser since the 2011 rule changes, the gases are guided down channels inside the rear wheels, sealing the gap between the tires and the outer side of the diffuser and this serves as skirt to seal the side of the diffuser from leakage. Having the exhaust blow along the diffusers edge keeps these pressure regions separate and prevent the tire squirt upsetting the diffuser. Preventing these effects means the diffuser creates higher levels of downforce at the high rear ride-heights and large degrees of car rake and is more efficient. And an additional benefit is it means the team can run a higher rear ride height, which effectively makes the diffuser larger and further increases it’s potential to make downforce."
-->>
http://www.formula1-dictionary.net/diffuser_blown.htmlund hier noch der coanda-effekt bildlich (eine von vielen versionen):
(rot=exhaust-plume; gelb:sidepod-airstream)
und desweiteren:
gut möglich ist auch die tatsache, dass ferrari den exhaust-plume splittet, und nur teilweise gegen den tire-squirt einsetzt!
dazu ein cfd-bild von sauber als erläuterung (die schwarzen pfeile habe ich als verdeutlichung des splittens eingefügt):
