Sidepod design and the Meredith effect

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bhall II
bhall II
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Joined: 19 Jun 2014, 20:15

Re: McLaren MP4-29 Mercedes

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Aaaaaaaaaand we've come full circle. lol

For ease of use, I think these are things upon which most can agree:

- Up and down the grid, F1 cooling tends to rely on a pressure differential to move air through the radiator. The alternative is using the brute force of inducted air, but that's not very efficient. What happens on the exit side of the pressure differential, however, is up for discussion.

- McLaren's mushroom suspension clearly aims to improve the efficiency of the diffuser. How the sidepod vents interact with the suspension is also up for discussion, though.

While it hasn't been discussed here in much detail, I'm of the mind that flyboy is 100% correct about the lift-reducing intent of the straight profiles of the sidepods found on the Mercedes, Ferrari, Red Bull, et al. It just makes sense, especially since the design in no way precludes ultimately using the vented flow for something, be it Meredith to both decrease drag and blow fast(er) air directly over the diffuser, or alternatively, to increase suction above the diffuser via low-velocity vented flow.
JimClarkFan wrote:I think I understand the concepts you guys are discussing in isolation, higher vents for meridth effect...
The location of the vents depend on what you want to do with them. But, Meredith, in particular, isn't location-dependent. As such, the vent on the F14T, for instance, could just as easily vent high-velocity flow for Meredith, low-velocity flow for diffuser suction, or it could just be a ---' vent, yanno?

Because I tend to gravitate toward multi-faceted approaches to inescapable dilemmas, I think Meredith makes sense, as it reduces drag, regardless of where cooling flow is vented, and if you vent it over the diffuser, the faster flowing air increases the pressure drop at the diffuser. It's the proverbial "two birds with one stone" solution, especially on cars with layouts like the Ferrari.

In further defense of Meredith (sorta) on the McLaren, I think the MP4-29's solution probably hybridizes two philosophies.

Image

As it relates to the intent of the design iteration seen above, the Gurney tabs on the outside of the vent should promote a more efficient (faster) extraction of vented flow as required for Meredith. The white structure within the vent, red arrow, should help guide that flow directly over the mushroom suspension, which we all seem to agree helps increase diffuser efficiency. In that way, the mushroom suspension is a veritable extension of the diffuser, and the vents use Meredith to blow faster air directly over it.

That particular iteration clearly hasn't worked, as it's been abandoned. But, I'm still of the mind that current philosophy remains the same; it's just being honed by additional work.

Unrelated: I think it's somewhat puzzling, if not ironic, that McLaren's best car in recent years has been the one for which the team did not employ a gimmicky design philosophy. Neither 2010's f-duct nor 2011's u-pods, or this year's mushroom suspension, have made for a better car than 2012's all-around solid design. (Then again, I guess that car did write the book for post-2011 EBDs.)

MANY EDITS: words

JimClarkFan
JimClarkFan
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Re: McLaren MP4-29 Mercedes

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Thanks guys.

Think I understand what you guys are saying

bhall II
bhall II
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Joined: 19 Jun 2014, 20:15

Re: McLaren MP4-29 Mercedes

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Well, that makes one of us! lol

It kills me to come up with a theory or two for which there's little chance of confirmation except for the hope Racecar Engineering might get its hands on the hardware a few years down the line. Otherwise it's hard to tell if one's "analysis" is genius or idiotic, though I suspect mine most often falls in the latter category. (But, it's still fun to pretend to be smart.)

JimClarkFan
JimClarkFan
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Re: McLaren MP4-29 Mercedes

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bhall II wrote:Well, that makes one of us! lol

It kills me to come up with a theory or two for which there's little chance of confirmation except for the hope Racecar Engineering might get its hands on the hardware a few years down the line. Otherwise it's hard to tell if one's "analysis" is genius or idiotic, though I suspect mine most often falls in the latter category. (But, it's still fun to pretend to be smart.)
Don't get me wrong, I still have no idea what is going on, but I am understanding what you are trying to say... just to clarify :mrgreen:

bhall II
bhall II
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Re: McLaren MP4-29 Mercedes

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Oh, I know that's what you meant. I just wanted to emphasize that I'm not entirely sure what I meant. lol

flyboy2160
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Re: Sidepod design and the Meredith effect

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Bumped for merged posts.

olefud
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Re: Sidepod design and the Meredith effect

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Powerslide
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Joined: 12 Feb 2006, 08:19
Location: Land Below The Wind

Re: McLaren MP4-29 Mercedes

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bhall II wrote: Otherwise it's hard to tell if one's "analysis" is genius or idiotic, though I suspect mine most often falls in the latter category. (But, it's still fun to pretend to be smart.)
:lol:

Those sidepods does not use radiators for heat expansion thrust but heat is diverted towards the top singular exhaust outlet whereby the exhaust travels in a much higher velocity. This would mean engineers are trying to vacuum out radiated air but with the most minimal diameter hole while the rest of the outlets are use to boost downforce. If you look closely at the pictures you posted, the side radiators and actually moved to side to clear way rather than to capture the majority of air flow. This majority flow is directed towards the rear diffuser, using the side pod intake to produce downforce at the diffuser rather than old school cool of radiators. Radiators are put to the side and air movement through them is via the exhaust vacuum.

Image

Don't see a radiator on Newey's side pod intake and that's because its all heading towards a diffuser. Rather interesting seeing flow-viz pointing towards the side pod inlet cough! cough!
speed

bhall II
bhall II
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Joined: 19 Jun 2014, 20:15

Re: Sidepod design and the Meredith effect

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I think the reason why you don't see a radiator in that picture is because of the angle in which it was taken. The cooling layout of the RB10 has the radiators/intercoolers mounted high within the sidepod.

Image
(Click to enlarge.)

If you look in the above image, you can see how the vents (roughly indicated by yellow lines) are situated behind the radiator, meaning they vent flow that has passed through the radiator.
Radiators are put [somewhere] and air movement through them is via the exhaust vacuum.
This is the pressure differential to which I referred. Cooling wouldn't be very efficient if the radiator wasn't encased within a plenum in which it divides the intake side (highlighted in light, transparent blue) from the exit side (formed by the inner engine cover and upper sidepod bodywork). Air flow follows the path of least resistance, so to speak, so if there was a way for cooling flow to pass around the radiator without ever passing through it, it would.

(There's a much better way to word that, but for some reason my brain can't see it except to know that it's there. I fink I wohke up missin a foo QI points twodae(

EDIT: fixed image link
Last edited by bhall II on 21 Jul 2014, 19:03, edited 1 time in total.

smellybeard
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Re: Sidepod design and the Meredith effect

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Long chord radiators just aren't efficient enough because of the build up of internal turbulence and high temperatures in the airflow, so the only way to get the required cooling is to use a shorter chord (thinner) rad and sit it diagonally in the pod. Clearly, you can see that diffusers are used to prepare the airflow for the rad and that the waste air is ducted away to do the least damage after it's used.

It's a practical solution and has been almost universal since the late seventies.

BTW, although the P-51 mustang is the popular example of the Meredith effect radiator installation, the Spitfire is the original. The spit's radiator (and intercooler radiator on later versions) is the full depth of the wing with only a small intake and exhaust protruding beneath. The high temperature cooling circuit of the glycol system employed by the merlin is particularly suited to such an installation.

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Powerslide
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Re: Sidepod design and the Meredith effect

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bhall, if you look closely, you will notice the horizontal line you drew actually escapes the radiators and come from within the shield. This is clear on that main picture that flow is coming from within the inner shield and on the outer side are radiators hinting that a lot of air is being flowed to feed rear the heavily finned rear for aerodynamic downforce advantages. I think this route became important since the banning of double diffuser and blown diffuser. This is their new toy
speed

bhall II
bhall II
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Re: Sidepod design and the Meredith effect

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Though it obviously doesn't mean it's not there, I'm just not seeing what you're seeing.

trinidefender
trinidefender
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Joined: 19 Apr 2013, 20:37

Re: Sidepod design and the Meredith effect

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These radiators would not work properly if airflow was allowed to bypass the radiators. The concept of markedly increasing the efficiency of radiators by ducting them to create a pressure differential has been established for a very long time.

Cold Fussion
Cold Fussion
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Joined: 19 Dec 2010, 04:51

Re: McLaren MP4-29 Mercedes

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bhall II wrote:
http://i.imgur.com/WU28oH1.jpg
Look at me actin' like I actually know what the hell I'm talkin' about.
Assuming the drawing is accurate, how does the flow stay attached in such a highly diverging diffusor? Does the high velocity air (on the order of hundreds of km/h) have a tendacy to stay attached despite the large angle?

trinidefender
trinidefender
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Re: McLaren MP4-29 Mercedes

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Cold Fussion wrote:
bhall II wrote:
http://i.imgur.com/WU28oH1.jpg
Look at me actin' like I actually know what the hell I'm talkin' about.
Assuming the drawing is accurate, how does the flow stay attached in such a highly diverging diffusor? Does the high velocity air (on the order of hundreds of km/h) have a tendacy to stay attached despite the large angle?
The flap is only opened that much for full power climbs, take-offs and high power slow speed flight. Which is pretty much clubs and takeoffs lol. At high speed the flap will be in its fully closed position and will actually be a converging duct. This is where the increase in velocity at the mouth of the exit of radiator duct comes from. This increase in velocity is what actually provides the thrust that they talk about when trying to explain the Meredith effect.