Exhaust Blown Floor - Forward Exhaust Exit

[ringo]

You mean 721 ft/s ?

The beginning of the European GP. In the first stint, i thitnk it was petrov who went into a streak of concrete dust laying across the track.
You can't miss it.

The exhuasts need to be as fast as possible for aero reasons. This is why they have nozzle shapes to accelerate the flow.





It creates back presure against the engine, but the aero gain is worth it.
The speed needs to come as close as possible to the speed of sound, as there is no reason not to.

[strad]

The beginning of the European GP. In the first stint, i thitnk it was petrov who went into a streak of concrete dust

Okay...I think this is what you're after.
I don't know how I got my clips screwed up but basically this is what is in the video:
a quick original shot, followed by reverse at 1/16 speed, fwd and then back frame by frame...slow forward at 1/16 and then reverse at 1/8.
It is a little slow loading because I used the Mpeg format to get as clear a shot as possible from my aging capture equipment.
I used the different speeds fwd and back because I think you see some things clearer.
I hope it helps...What I notice is there doesn't seem to be any/much? dust coming out the back/diffuser.
Click Here:
http://www.stradsplace.com/VIDEOS/2011S ... v-dust.mpg

[hollus]

Thanks a lot Strad. That video helps very much indeed!
If anybody (like me) had problems, seeing it, try "save link as".

[marekk]

The problem with concrete dust (not unlike water droplets in rainy Turkey this year) as a reference is we actually still don't see pathlines of exhaust gases.

But one thing is obvious - exhaust gas moelcules are much, much lighter then water droplets (not to mention concrete dust particles), so they loose momentum much, much quicker and all of the gases are inside this visible water/dust curtain.
One can't expect shotgun blast gases to reach further then the bullet.

To follow more closely actual exhaust pathlines, we need much finer marker, burnt oil smoke being the best available.

But those damn enegines are to reliable We have still to wait for the ultimate evidence.

[Formula None]

Nice vid, strad. This looks like a mid speed corner (?), total guess, maybe ~100mph? Compare exhaust trajectory to when its standing still. What's it look like at 150mph? 200? What speed were they optimizing this FEE for?

[ringo]

The problem with concrete dust (not unlike water droplets in rainy Turkey this year) as a reference is we actually still don't see pathlines of exhaust gases.

But one thing is obvious - exhaust gas moelcules are much, much lighter then water droplets (not to mention concrete dust particles), so they loose momentum much, much quicker and all of the gases are inside this visible water/dust curtain.
One can't expect shotgun blast gases to reach further then the bullet.

To follow more closely actual exhaust pathlines, we need much finer marker, burnt oil smoke being the best available.

But those damn enegines are to reliable We have still to wait for the ultimate evidence.

i haven't seen the video yet but i can assure you, dust is lighter than flow vis.
So you wont get a better representation than that.
It's downloading,I can't wait to see it.

edit: look from 2:17 in the video.

The dust is being pushed away, not sucked under every one observes this?

Waiting on Shelly to chime in after he/she has watched the video objectively.

[shelly]

ringo, it would be nice to dicsuss if you would read my posts.
As I wrote before, and as marekk also wote later, dust is not light enough to make a reliable flow vis, as isn't water.
Or do you expect air to be drawn as high as water clouds from the track in the wet?

[Formula None]

Not sure I follow, shelly. You can see the exhaust pulses affecting the dust outside the floor. Is this not the gas stream? What are you suggesting? How visible would sound waves be in this dust cloud?

[shelly]

Dust has more inertia than hot air, so dust trajectory is different from that of the hot gases

[Formula None]

How much inertia can a fine dust mote or water droplet have before being overcome by, I assume at this scale would be, viscous forces?

[shelly]

it is not viscous forces, it is inerita forces.
You have to compare density: a droplet of water is 1000 heavier than a particle of ambient temperature air of the same size; ratio goes to 2000-3000 if air is hot. Dust is heavier than water

[strad]

The important thing to note is that nothing comes out the back..it is pushed away and down the side of the sidepod...once again re-enforcing the idea of a seal/aero-skirt

[shelly]

The important thing to note is that nothing comes out the back..it is pushed away and down the side of the sidepod...once again re-enforcing the idea of a seal/aero-skirt

The importantant thing to note is that if we watch dust we are seeing where dust goes, and not where exhaust goes. Gas and dust trajectories are different

[strad]

The dust will follow the exhaust gasses..they are what is moving the dust therefore the dust has to move along the same lines if somewhat slower and not as far.

[shelly]

The gas are moving th dust, but they do not follow the same path: as you say, the dust is slower and does not follow the gas.