Aerodynamic implications of nose inlets

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.

Post Mon Feb 13, 2012 4:53 pm

Twaddle wrote:
Adrian Newby wrote:I'm sure all of the designers are far too clever to agree with me.

It's all a matter of trade-offs, so what are you willing to give up to get a little less drag on the nose of your car?

All air is critical, but some is far more critical than others.

The fences only extend as far as the hump, at which point an air dam is going to spill off to the sides as it builds forward (a goodly portion of the oncoming air running into the air dam would have already spilled off to the sides). And if that is as large as your air dam is going to be, I don't see the point, especially for the cost to the flow on the sides. I believe the fences are there to keep the air that is going up the ramp from being pushed over the sides.

Continue to differ with me all you like. It will put you in far better company!


I'm going to have to agree that it seems more likely for the top slot to be a vent than a dam.

You have a rule that would generally lead to a stepped nose if you want to maximise the underbody airflow. Other than being ugly, one of the main disadvantages of the step would be air spilling around the sides causing disruption in an area where you gain considerable benefit from keeping the flow as clean as possible.

Inserting a vent into the area where the step would be reduces this disruption while also scavenging some additional cooling air at virtually no cost; win/win. (Obviously we can't tell if they've managed to duct some of this air to provide additinoal KERS cooling, or if it's just servicing the driver and electronics.)

If you have an air dam that creates a large enough effect to be significantly better in terms of aero efficiency than a simple step, for air flowing over the nose, I don't see how it could do anything other than create increased "side-spill"; win/lose. I know which one sounds like the better option to me.

It would be good if someone could run some CFD with a detailed reproduction of the RB front end modelled as both a dam and a vent at some point to see how things look. Either way it looks like those side slop "fences" would be important in keeping the flow clean on either side. Apologies if n_smikle's work included these(I can't see it for some reason), but it sounds like it didn't from the discussion.


P.S.
Adrian, I'm going to go out on a limb and suggest that some people are being put off reading your posts as clearly as they might due to the agressive tone you seem to favour. Combined with your earlier post mentioning "equal transit time" in relation to Bernoulli's principle (which was never going to do your credibility any favours) it's not going to lend much weight to your ideas. I know it doesn't help me to read your posts objectively when you're basically coming across more like you're preaching than raising points for discussion.


Sorry if I put anyone off. I know I do get a little/lot preachy. Just be glad you aren't one of my kids!

You're probably not going to like this next bit any better...

I am so freaking tired of Bernoulli. I tried to explain a simple lift concept to someone who sounded like they had never heard of such a thing before, and immediately got jumped on (and still do, daily) for bringing up Bernoulli.

Sorry, but Bernoulli's principle is a part of science history. Sure there have been better explanations since then, but there have been in every field. Long-winded explanations are beside, and beyond, the point at hand. I explained Bernoulli's principle in the most simplistic way possible on purpose, not because I don't know more advanced and modern thought on the subject. Do you tell a small child he needs to create a certain slip angle when he is wanting to turn his tricycle? I'm not saying people on this board are children, but what I am saying is that there is no need to go that far in depth about the thing you need someone to know, for them to have a basic idea about it, so you can get on with it and make your actual point about something else.

In any case, people got far to upset far too fast, so I get the distinct impression that this whole Bernoulli fracas has more to do with other people and some long-running fight they were having with someone else. So, at the expense of derailing the thread, they jumped out there and started their fight up again, thinking they would use me as their whipping boy for their "cause".

But "That ain't me, Babe", as Dylan would say...
Adrian Newby
 
Joined: 7 Feb 2012

Post Mon Feb 13, 2012 5:14 pm

As far as the "bernoulli issue", to which probably I contributed, I did not want to cause any mess, but I think if you try to explain something you know about,then using simplified but wrong examples is not a good idea.

These threads are full of aerodynamic wrong simplifications and miths which are difficult to debunk and make discussions long and twisted.

That said, who were the posters giving you the distinct impression of using this thread to start a fight?

edit: I have seen now the chat between you and kilkoo316
Last edited by Steven on Thu Feb 16, 2012 12:34 am, edited 1 time in total.
Reason: Removed personal comments
twitter: @armchair_aero
shelly
 
Joined: 5 May 2009

Post Mon Feb 13, 2012 5:58 pm

I guess it has been a while since I have been in a basic science class. They don't discuss Bernoulli as a basic intro to lift anymore? I guess they no longer use the onion theory of education. Maybe they start at the quark and build everything up from there now. I never thought of the scientists who came earlier as being "wrong", as much as I thought they just didn't have that information available to them yet... that the ones who came later stood "on the shoulders of giants" and all that...
Last edited by Steven on Thu Feb 16, 2012 12:35 am, edited 1 time in total.
Reason: Removed quoted post right above
Adrian Newby
 
Joined: 7 Feb 2012

Post Mon Feb 13, 2012 6:26 pm

Adrian Newby wrote:I guess it has been a while since I have been in a basic science class. They don't discuss Bernoulli as a basic intro to lift anymore? I guess they no longer use the onion theory of education. Maybe they start at the quark and build everything up from there now. I never thought of the scientists who came earlier as being "wrong", as much as I thought they just didn't have that information available to them yet... that the ones who came later stood "on the shoulders of giants" and all that...

People here don't have a general problem with Bernoulli (that I'm aware of anyway) and I don't see any reason why they should. The problem was that you said the air goes faster over the top (classic example of a plane wing, not a car wing) because it has further to travel and needs to rejoin the flow underneath. It's the bit in bold that's a problem, because it's simply not true.

Saying that the air goes faster over the top resulting in lower pressure on the upper surface is fine. What's not fine is saying that it's because the flow needs to take the same time to travel over the top as it does to travel underneath. "You should strive to make things as simple as possible, but no simpler" or something to that effect, cba to look up the exact quote. People get annoyed about this one in particular because it's so frequently repeated
Twaddle
 
Joined: 17 May 2010

Post Mon Feb 13, 2012 6:51 pm

Twaddle wrote:
Adrian Newby wrote:I guess it has been a while since I have been in a basic science class. They don't discuss Bernoulli as a basic intro to lift anymore? I guess they no longer use the onion theory of education. Maybe they start at the quark and build everything up from there now. I never thought of the scientists who came earlier as being "wrong", as much as I thought they just didn't have that information available to them yet... that the ones who came later stood "on the shoulders of giants" and all that...

People here don't have a general problem with Bernoulli (that I'm aware of anyway) and I don't see any reason why they should. The problem was that you said the air goes faster over the top (classic example of a plane wing, not a car wing) because it has further to travel and needs to rejoin the flow underneath. It's the bit in bold that's a problem, because it's simply not true.

Saying that the air goes faster over the top resulting in lower pressure on the upper surface is fine. What's not fine is saying that it's because the flow needs to take the same time to travel over the top as it does to travel underneath. "You should strive to make things as simple as possible, but no simpler" or something to that effect, cba to look up the exact quote. People get annoyed about this one in particular because it's so frequently repeated


As I have said, repeatedly, I made my explanation overly simplistic on purpose because it was intended for someone I thought had no exposure to lift, and I wanted to get on with the point I was actually trying to make. There are a great many things we all learn and know which are technically incorrect, but they serve us well until we are better able to understand things at a deeper level. It is called the onion theory of education. It has been used for thousands of years. "People get annoyed..." implies I was correct that I stumbled into someone else'e previous argument.
Last edited by Adrian Newby on Mon Feb 13, 2012 7:01 pm, edited 1 time in total.
Adrian Newby
 
Joined: 7 Feb 2012

Post Mon Feb 13, 2012 6:55 pm

And another thing...

I never said the streams would have to rejoin. And not long after my infamous "Bernoulli" post, I specifically said that the flow doesn't always rejoin, and even gave examples of it.

What I actually said was that the stream going over the top would have to go faster to get to the back of the wing at the same time as the stream on the bottom - which is a true statement of mathematical fact - if something has farther to travel it must go faster if it is going to get there as quickly as something traveling a shorter distance.

Also, I said in the post that I was talking about an airplane wing, not a car wing.

Yet this continues to linger. Which is most ironic since the whole point of giving a simplistic explanation was to get through it as quickly as possible so we could talk about the actual topic of the thread.

I am done with this. I have been done with this. Everyone else keeps bringing it up. Is it really that interesting? Do we need to move it to its own thread?
Adrian Newby
 
Joined: 7 Feb 2012

Post Mon Feb 13, 2012 11:34 pm

Adrian Newby wrote:Bernoulli's principle.

An airplane wing has a larger curve on the upper surface than on the bottom. Imagine two streams of air, one going over the wing, the other going under it. The stream going over the top must go faster to get to the back of the wing at the same time as the stream on the bottom. The faster velocity on top results in a decrease in pressure, which lifts (sucks) the wing upward.


No one is arguing that you were trying to simplify things. It's usually a good method to take. The only thing people have issues with is when you simplify something by describing something that is NOT true and perpetuating myth. A few users have politely posted attempting to explain to you what the issue is, and you refuse to acknowledge that you may have mispoken. Instead of arguing so much to the point that you are not listening to what they say, just take a step back and admit that you may have made a small mistake and everyone can move on from this.

Re-read what I quoted above that started this all, and you'll see that you (accidentally?) said something that was not true. Even if you do have a very good understanding of aerodynamics, others do not, so it helps not to explain Bernoulli in this way. Bernoulli's principle is true. Bernoulli's principle is useful in describing the basics of lift. But Bernoulli's principle in no way says the stream on top and the stream on bottom get to the back of the wing at the same time.
volarchico
 
Joined: 26 Feb 2010

Post Tue Feb 14, 2012 1:27 am

My late 2 cents on this topic:

Rough and dirty estimation of added drag at 100m/s for both solutions will be about 20-30N (RBR's slightly higher), compared to about 7000N of the whole car. Not a big deal, but the teams are ready to spend serious money on aero developement if they see more then 0,001s/lap gain, so i wouldn't say it's that unimportant either.

BL on the top surface:

McLaren keeps the whole thing convex, and this helps big time - even small radius has big influence on BL buildup and laminar-turbulent transition.

Others (with RBR exception) have two almost flat sections connected with (more or less agressive) ramp, which forms highly concave shape in the direction of the flow - this means almost always rapid grow of laminar BL and quick transition to turbulent, which may or may not relaminarize after the ramp. Skin friction coefficient on the ramp could be easily 10 times that of flat surface.

RBR's solution (vented or not) with stagnation point in front of the lip, keeps the BL's over the whole top thin, laminar and less draggy in every cirumstances simply by dividing it.
If there are any vents under the lip, then with right shape of the ducting and by placing the outlet(s) carefully one can even get some suction at inlet (makes even more sense for the vents under the nose, far more critical for the performance of the car).

Air dam - don't think such thing exists in our universe.
Fluids are not bunch of bullets, one cannot just stack them in front of a wall with a hope they'll make the flow above to pass nicely above them.
I would rather expect all sorts of backflows and eddies formed in such region.
marekk
 
Joined: 11 Feb 2011

Post Tue Feb 14, 2012 4:21 am

volarchico wrote: take a step back and admit that you may have made a small mistake and everyone can move on from this.


My. God.

Really? You are really going to bring up this again?! And not only that, you are going to highjack this thread with this garbage until I confess that I have been a naughty boy? :roll:

And then you will let everyone "move on" from this tragic moment in aerodynamic history? You will be kind enough to do that for us? [-o<

It's cute that you think you are the internet police, or is it the Bernoulli police?

Absolutely incredible.
Adrian Newby
 
Joined: 7 Feb 2012

Post Tue Feb 14, 2012 4:56 am

And since you refuse to let this die...

I did not mis-speak. I said exactly what I meant to say. Just as I have said before, there are a great many things in this world that are not technically correct that we are all taught, and that serve us well until we delve into them deeper.

You just happen to have a problem with this particular one. That is your problem, not mine.

So where does this end? How uptight do you want everyone to be about things? When you are riding in a car with someone who is going into a corner too fast, do you yell "Accelerate! Accelerate!"? Why not? That is technically correct. Braking is just an acceleration in a different direction.

How about you make your own decisions and I'll make mine. (note the distinct lack of a question mark)
Adrian Newby
 
Joined: 7 Feb 2012

Post Tue Feb 14, 2012 4:58 am

Everyone learns in different ways, and because of that, it's not at all uncommon that people with the same knowledge have found their way to that knowledge with an entirely different map, so to speak. For me, Bernoulli's principle, with regard to wings, conjures up a mental image of the wing's curved side stretching out the air passing over it so that the rest of the wing can follow along and fit in the space that the stretching created. It wasn't explained to me that way, nor have I ever seen it explained that way, but it's not wrong insofar as it gives my brain a simple picture of the essence of the concept.

It's only natural that folks from all over the world who "meet" on the Internet to share knowledge have followed entirely different maps to reach that knowledge. And I think that's a beautiful thing, but you have to be open enough to see it.

I guess the point I'm walking around is this: there's no difference between the intractability of someone who only teaches one way and the intractability of someone who only learns one way. They're both equally dense, and one complaining about the other is hypocrisy. "Pot, kettle. Kettle, pot."

I don't know. It's something to think about.
Last edited by bhall on Tue Feb 14, 2012 5:01 am, edited 1 time in total.
bhall
 
Joined: 28 Feb 2006

Post Tue Feb 14, 2012 9:28 am

Adrian Newby wrote: I keep trying to move on and get back to the topic at hand



Let's go then. Like many others here I think that the main aim of the slot over the nose is about external aero effciency. I do not knowhre tha air in the inlet goes, what it cools etc, I think, like others, that the vent is there mainly not to make air go elsewhere.

Two most important points in my view:
-making the boundary layer start new from the leading edge above the slot
-avoiding air spill form the sides in the form of vortices, badly interacting with the push rod pin point. I think ferrari can afford a vanilla ramp because they have no pushrod. Because of this, I think that the advantage of such a solution is 3dimensional.

The convex shape before the slot is for forcing a bit of pressure recovey and guide the flow inside the slot better.
twitter: @armchair_aero
shelly
 
Joined: 5 May 2009

Post Tue Feb 14, 2012 11:04 am

It seems to me that the air thru the slot, above a certain speed, stalls and spills around the sides. What air does make it thru probably does cool something. Most probably the KERS unit.
Don't one of you guys have one of them fancy flow programs? :lol:
"To race is to live. But those who
died while racing knew, perhaps,
how to live more than all others."
~ Juan Fangio
strad
 
Joined: 2 Jan 2010

Post Tue Feb 14, 2012 12:00 pm

Once my initial impression of the slot's purpose was justifiably marginalized, I went along with the idea that it likely combines with the lower slot under the nose to sufficiently cool Red Bull's problematic KERS.

But, now I'm wondering what part of KERS is even in the nose to be cooled. I was under the impression that KERS components are (generally) placed in the sidepond(s), under the fuel tank and just ahead of the engine. (And something is making me think Red Bull reportedly placed one of those at the very rear of the car. But I might be making that up.)
bhall
 
Joined: 28 Feb 2006

Post Tue Feb 14, 2012 1:00 pm

Well, I think that this thread has just shown up the best and the worst of f1technical.net

As for the worst, well, there seems to be a lot of wasted effort going on. I once read a Chuang Tzu quote in a great textbook that said,

Words are for meaning: when you've got the meaning, you can forget the words.


I think the scientific community is obsessed with semantics and, although I understand the need for standardisation, I think people forgot to attempt to grasp the meaning of what others are saying before they criticise the language they have used.

Anyway, on the plus side, this thread has given me some interesting insight into F1 car design, particularly regarding boundary layer formation. It seems to me the car is designed to generate significant amounts of turbulence on purpose, but then aerodynamically turbulent flows are less useful (for lift generation), so are there efforts to maintain laminar boundary layers where possible? I guess, particularly when following another car, there may be no chance of forming a laminar boundary layer as the oncoming flow would trip it anyway.

All very interesting concepts (including the nose slot - can I call it a "glove box"?). More of the good stuff please.
"Words are for meaning: when you've got the meaning, you can forget the words." - Chuang Tzu
horse
 
Joined: 23 Oct 2009
Location: Edinburgh, UK

PreviousNext

Return to Aerodynamics, chassis and tyres

Who is online

Users browsing this forum: CCBot [Bot] and 3 guests