Exhaust Blown Floor - Forward Exhaust Exit

[Javert]

Javert.. listen to this video very carefully. This whole issue of blowing the flow has to be handled calmly and carefully. There are many inaccurate F1 videos around, yes, even those made by somebody in the Pirrelli PR department.

[youtube]http://www.youtube.com/watch?v=PDWFaRVQ ... r_embedded[/youtube]

Understood

[marekk]

This is inconsistent with some arguments made on here...



But it's simply the car driving over some smoke. THat happens to be on top of the floor as well!

You need to be calm in these situations. Anxiety can often lead to quick and wrong decisions.

This smoke comes from overheated and burning leading edge of the floor - just opposite to exhaust outlet.

It's not very high reving at the moment, but is not idling either - those cars don't go 80 kmh with idle engine on 1st gear. My guess is around 12krpm.

Visible smoke particles, if not perfect, are still the best marker we can ever see, and introduced to the flow they can make it clearly visible. That's how all wind tunnel test are done.

If the flow goes outwards - as on my first screenshot, low pressure inside this flow makes them follow flow's pathlines.

The same for moving car. All along the pitlane, and even as Heidfeld starts to accelerate on pit lane exit, there is no evidence of smoke outside of left rear tyre.
For me this means that (almost) all exhaust gases go out between rear tyres - under and over the floor.

[wesley123]

How can you state that when the whole bodywork is burning causing the smoke? This has in no way to do anything with the exhaust, apart from that the smoke has almost no power to the blast, where the exhaust can blast something like 2/3 metres far?

Rubbish assumption if you ask me

[malcolm]

How can you state that when the whole bodywork is burning causing the smoke? This has in no way to do anything with the exhaust, apart from that the smoke has almost no power to the blast, where the exhaust can blast something like 2/3 metres far?

Rubbish assumption if you ask me

I disagree.

The only part of the bodywork that is burning is that which is experiencing very hot exhaust gases flowing over it.

Therefore, that bodywork is releasing smoke into the stream of exhaust, and would therefore provide a visualization for that exhaust stream.

It's not like the side of the sidepod was smoking...





Of course, what we need is a shot taken during max rpm after he leaves the pits, and before he slows down due to the fire... so far we only have a low-rpm/speed-limiter situation with minimal exhaust flow, at relatively low speeds.

[wesley123]

Rubbish, this is smoke coming off the body work, it isnt blown off the bodywork like the exhaust blows, due to the power of the exhaust it will blow much wider, like Ringo's CFD shows. To asume the exhaust flow has the same flow as the smoke coming of the bodywork is just untrue.

You are clearly forgetting the power which exhaust gasses get blown outwards

[malcolm]

So you are saying that the smoke that is being generated by the hot exhaust flowing over the bodywork will follow the exhaust stream for a short while, and then decide that it would rather traverse that exhaust flow and head down the side of the sidepod rather than continue with the exhaust?

Just wanted to clarify exactly what you think is rubbish...

[strad]

Let's see..it comes out like this..
click for video

where at speed it turns into something like this..
click for video

that flows along the sidepod forming a seal and just to the inside of the tire.

[wesley123]

So you are saying that the smoke that is being generated by the hot exhaust flowing over the bodywork will follow the exhaust stream for a short while, and then decide that it would rather traverse that exhaust flow and head down the side of the sidepod rather than continue with the exhaust?

Just wanted to clarify exactly what you think is rubbish...

I always thought smoke from a fire just came off bodywork and wasnt thrusted off it.

Please, just think. How can exhaust flow, that comes out the exhaust at around 600kph 90 degrees to the cars longitudinal have the same route as smoke that just detaches from it's material that is on fire? Somewhere between the law of physics and simple logic it tells me that cannot be right

[N12ck]

It has been confirmed by renault that a new engine mapping ran in qualifying or practice had caused a crack in the exhaust, they didnt know, and during the pit stop which was rather long one fuel built up and it ignited the crack expanded and the fire started burning the bodywork, google news it, you will see for yourself

http://www.topgear.com/uk/car-news/nick ... -2011-08-4

[ringo]

A crack hmm.

So the pipes are running too thin for their lenght.

[malcolm]

Wesley,

I guess it all depends on what part of the bodywork is smoking.

If it is in the 600 km/h exhaust stream, certainly that smoke would be accelerated by the exhaust stream and rather closely follow its trajectory.

If it is originating from beside the exhaust pipe near the exit (i.e. due to the crack), then it may follow a different trajectory.

Need to find that out first.


However, it does show that some smoke that is outside of the confines of the floor does end up going under the diffuser, irrespective of where the exhaust goes. This was a major sticking point earlier in the thread.

[hardingfv32]

Is there anything surprising about the smoke going under the floor? It is a low pressure area and there is no positive seal on the sides.

Brian

[malcolm]

Not to me... ask Ringo.

[Edis]

A crack hmm.

So the pipes are running too thin for their lenght.

The exhaust system is normally made of inconel 625 sheet with a thickness of a few tenths of a mm. Due to the high operating temperature, thermal cycling and vibrations the pipes can suffer from fatigue and creep.

[shelly]

"We also know that the forward exhaust, by contrast, performs more strongly once the rear ride height starts to compress"

Discuss