Diffuser Confusion

[shelly]

Agree with just a fan, except for the function of fences, which are also vortex generators.
In this picture we have a nice shot of the diffuser kink line raptor22 refused to believe in.
@vonk: I suggest you go through the thread "how does a diffuser function", a lot of stuff is discussed there and would be beneficial to this discussion - I think the two threads should be merged

[Ciro Pabón]

Vonk, I love simple questions. This one rocks. Thanks. I'll keep an eye in this thread and study as much as I can, I want to contribute.

[xpensive]

Vonk, I love simple questions. This one rocks. Thanks. I'll keep an eye in this thread and study as much as I can, I want to contribute.

There you go Ciro, we can't have inough diffuser threads, can we now? While there's nothing like repeating rudimentary Bernoulli principles over and under and beneath and...all to the vain benefit of even the forum's most independent thinkers.

[hardingfv32]

Concerning the concave diffuser shown in the last photo....

While I do not question that it functions in this system, I do question the explanation given for its use. Usually you we see convex shapes to help with flow attachment in this situation. In all the studies I have reviewed, I don't recall ever seeing a concave diffuser shape.

Could the DDD design be introducing some other compromise or requirement? Was this diffuser blown?

Brian

[vonk]

Vonk

Maybe it would be easier to dispel what YOU think is going on in this area of the car.

So, I assume that you AGREE that there is down-force being generated by this system most of us are calling a diffuser. What is your explanation for how the down-force is being generated.

Your first post mentioned flow above the diffuser. Is this your main theory?

Brian

Brian,

I agree that the apparent purpose of the diffuser was to add down-force. I wonder whether more-than-deserved credit was given to the diffuser when it first appeared, because the car it came on was so much faster than the others. When the others put on diffusers they still couldn’t catch up. But it appeared to be of benefit, even operating under such adverse conditions. I’m sure that its optimization became an expensive black art of cut and try.

You can see from my original posts that I am looking for other benefits form the diffuser such as upward deflection of body slip stream. That slip stream traverses a lot of turbulence-creating suspension components, and maybe, just maybe, its upward deflection can clean that up a bit, besides adding some down force. Could the diffuser assist in other wake management, etc, etc, etc?

As you can see, I have no main theory. But I believe that we should not be misled by the many standard explanations in the interested community, based on simplistic application of closed system flow theory to the complex conditions of an open system race car. – End of speech.

[xpensive]

Good Lord, can't believe I was taken by vonk-er's goobeli-gook for a while, he's just a troll for crying out loud!

"upward deflection of body slipstream", s**theels...but congrats, you got your 15 minutes...

[hardingfv32]

You mean: I don't understand any of this so it must be too complex for me?

Why start a thread and give up on it? So this is trolling?

Brian

[Just_a_fan]

Concerning the concave diffuser shown in the last photo....

While I do not question that it functions in this system, I do question the explanation given for its use. Usually you we see convex shapes to help with flow attachment in this situation. In all the studies I have reviewed, I don't recall ever seeing a concave diffuser shape.

Could the DDD design be introducing some other compromise or requirement? Was this diffuser blown?

Brian

Another example of a concave diffuser:


I'm not sure I've seen an F1 car with a convex diffuser ramp for ages...

[xpensive]

Sorry harding, I completely misunderstood you there.

[hardingfv32]

"I'm not sure I've seen an F1 car with a convex diffuser ramp for ages..."

Why?

Doesn't the flow in the diffuser need to stay attached for optimum effect? How does a shape bend at bend at the throat help? I am speaking of the diffuser in isolation with these questions. I appreciate that the concave design has benefits for the system in total.

Brian

[vonk]

Another example of a concave diffuser:


I'm not sure I've seen an F1 car with a convex diffuser ramp for ages...

I can't recgnize a concave diffuser in this picture.

[horse]

I wonder whether more-than-deserved credit was given to the diffuser when it first appeared, because the car it came on was so much faster than the others. When the others put on diffusers they still couldn’t catch up

F1 cars have had diffusers for 30 years. The ground effect cars were effectively large diffusers, if you want to think of it that way. There was no deflection to the flow over the top of the car, it was all done underneath.

If you're talking about the double diffuser on the Brawn GP then it was faster because it was larger than the diffusers on the other cars and the entire car was designed around having a bigger diffuser. The lack of basic design about this concept was why many other teams failed to catch them up that year.

@vonk: I suggest you go through the thread "how does a diffuser function", a lot of stuff is discussed there and would be beneficial to this discussion - I think the two threads should be merged

Shelly I think this thread is nonsense and should be locked or deleted and so I've reported the original post.

[Just_a_fan]

Another example of a concave diffuser:
[img removed as it's already obvious which one we're referring to]

I'm not sure I've seen an F1 car with a convex diffuser ramp for ages...

I can't recgnize a concave diffuser in this picture.

Look at the rear wing endplate with the 3 on it. Go down from the 3 to the diffuser. The outer section of the diffuser is concave (you can see a highlight on the upper surface showing the curve which, for the airflow below, is concave). The inner section (below the centre line of the wing) is actually convex so I should really have said "I can't remember the last time I saw a purely convex diffuser".

[vonk]

Remember the Kamm Tail?



How about a “Kamm Diffuser”?



Is this what’s going on here?



If this is indeed a “Kamm Diffuser”, I suspect it might be more self-adjustable to varying speeds.

All pure speculation!

[Giblet]

I think that pic is playing tricks with the eyes. I can not see where that 90 degree part is on the right side.