For the experts out there on diffusers...

[Mike]

I was on the beach and took this photo.....



Now for your exam question.

Explain the reason the dirt has settled round the edge of the diffuser at the bottom, and in the centre on the spoiler. Also, explain the reason for the water lines going from the outside inwards at the bottom of the diffuser. Use diagrams and arrows if necessary.

 

[Jason]

No idea,

But its a really good picture. hmy:

 

[Liambo-201]

Great picture Mike, and after our little conversation Sunday i was just waiting for you to ask this question on here

 

[Mike]

Great picture Mike, and after our little conversation Sunday i was just waiting for you to ask this question on here

Well you sir are a legend and I hope we can discuss it further in July

Pic was taken in a place called Glenelg. Google earth it and check out how rural it is

 

[Jonesy]

isnt got something to do with the air swriling behind the car because of the diffuser?

 

[ben_r1]

Lol a little extra time on your hands?

 

[slime]

...its all about pressure (down force)....the wing and difusser work to pull the car towards the ground and so the air (containing the dirt and water) will be sucked onto the underside of the spoiler and the point of lowest pressure on the diffuser.....or summat like that....a bit like the pressure clouds on fighter wings and aero's of a fighter jet.....this shows that the diffuser and spoiler is doing its job to a certain extent, although I doubt there is enough down force to make a great del of difference.....it's not a real F1 car after all!!

 

[Robo_#1]

No idea,

But its a really good picture. hmy:

What he said

 

[Mike]

...its all about pressure (down force)....the wing and difusser work to pull the car towards the ground and so the air (containing the dirt and water) will be sucked onto the underside of the spoiler and the point of lowest pressure on the diffuser.....or summat like that....a bit like the pressure clouds on fighter wings and aero's of a fighter jet.....this shows that the diffuser and spoiler is doing its job to a certain extent, although I doubt there is enough down force to make a great del of difference.....it's not a real F1 car after all!!

You'd definately get some marks for that, but you'd get extra marks if you included a diagram and arrows. Points are deducted for slang talk such as "summat" and punctuation

I'll give you a grade C for your answer, as I only partly understand the reasons lol.

Thank you though, I am enlightened (a bit)

 

[Paul]

IMO the air not only flows from under the car but also around it, the exhaust gases cause turbulence as it doesn't flow as evenly out of the pipes (thats why F1, Le mans, German touring cars etc have side exit exhausts), it also causes a greater volume to be in the 2 outer channels. When this meets the air form the side it causes mud to stick lower down i.e. where it leaves the car. With the centre 3 the air car leave more cleanly and goes where it should do - upwards - to leave a cleaner profile throught the air, thats why all of our rear windows end up caked in crud and in your case it hits the underside of the spoiler with it being horizontal everything else get inline with the roof and is blown on tho the car behind lol!

Thats just my take on it, im no expert so I hope it makes sense lol!!!

 

[Mike]

*You must also show any workings out you made to get your answer



Slime and F1team are both legends too. Good answers from both of you

 

[Paul]

*You must also show any workings out you made to get your answer



Slime and F1team are both legends too. Good answers from both of you

Lol ill do some pretty pictures when I get home from work - just for brownie points!

 

[harleybarley]

The way a diffuser works is by speeding the air up underneath the car, creating a region of low pressure, i.e sucking the car to the floor.

the reason the muck has settled on the underside of the spoiler in the centre and just above the exhausts is because:

The shape of the slots in the diffuser cause the air to flow upwards into the low pressure zone behind the car created by the hole the car cuts into the air, the reason it is only settling in the middle of the spoiler is because the flow from the edges of the diffuser is interrupted by the exhaust outlets, causing eddy currents where the flow becomes detatched from the diffuser surface and becomes turbulent (swirling).

In the centre of the car, the air is still attached to the diffuser surface causing it to flow upwards into the low pressure area behind the car i mentioned earlier.

the backlight angle of the car (the shape of the rear of the car) will also affect the flow of the air from the edges of the diffuser, where the flow detatches from the side of the car, vortices are created, which, along with the exhaust pipes, disrupts the flow around each side of the diffuser.

i hope that makes sense, it was wirtten quickly at work.

 

[Swervin_Mervin]

I'd wager it's got very little to do with the diffuser and spoiler and just the relatively bluff end of the car. (apart from the stuff on the actual diffuser and spoiler obviously)

In a wind tunnel you'd likely see the airflow even on a boggo 1.2 wrap inwards at the tail. You're forcing the air around the car so it's naturally going to come back 'together' at the other end.

 

[Mike]

OMG all these answers are giving me a headache

 

[harleybarley]

well you asked!

 

[Mike]

I know I know hehe, I expect someone will want to post a molecular diagram of the airflow - that WILL be interesting!

 

[harleybarley]

here we go,



CFD of a diffuser

 

[N0ddie]

The answer is....... just because.

 

[Foxspeed]

shows the rear diffuser works