Vodafone McLaren MP4-27 Mercedes

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Post Thu May 03, 2012 6:12 pm

hardingfv32 wrote:Why bother with with the end plate above the main element? Is it requiered by the rules?

Why doesn't the end plate seal the bottom of the second element/flap? I though that an end plate on the low pressure side of a wing was always a benefit.

IANAA, but... my bet would be that the luvres encourage the air flow out of the side of the wing to be upwards, and create an extension of the wing to the sides, wheras if you had no end plate air would spill off the high preasure side of the wing sideways (rather than upwards and sideways).
beelsebob
 
Joined: 23 Mar 2011
Location: Cupertino, California

Post Thu May 03, 2012 8:30 pm

There are no gurneys of slots in the floor, it's cabling for their sensors being run on the floor and covered with black tape.
GrizzleBoy
 
Joined: 5 Mar 2012

Post Fri May 04, 2012 12:13 am

beelsebob wrote:my bet would be that the luvres encourage the air flow out of the side of the wing to be upwards, and create an extension of the wing to the sides, wheras if you had no end plate air would spill off the high preasure side of the wing sideways (rather than upwards and sideways).


Not a bad thought. May I assume that these louvers in all cases provide less downforce or is there a chance of a net gain ASSUMING that the AoA is the same?

I appreciate that the louver might allow for higher AoA.

Brian
hardingfv32
 
Joined: 3 Apr 2011

Post Fri May 04, 2012 12:26 am

hardingfv32 wrote:Why bother with with the end plate above the main element? Is it requiered by the rules?

Why doesn't the end plate seal the bottom of the second element/flap? I though that an end plate on the low pressure side of a wing was always a benefit.

Brian

The endplates increase the downforce produced by the wing by effectively fooling the system in to thinking the wing is longer than it is. This is because the inevitable vortex produced at the wing tip reduce the downforce of the wing. It, in effect, makes the wing behave as if it were a shorter span. The endplates reverse this effect and so mean the wing produces more of its theoretical lift. We see these on airliners too in the form of vertical wingtips.

Unfortunately, the whole rear wing system still produces a big vortex at each end which creates big drag. So the teams use the louvres and the cut out behind the flap to reduce these large vortices. This will reduce the downforce but it improves the overall efficiency of the system. It's about efficiency. A more efficient system gives the teams more options.
Just_a_fan
 
Joined: 31 Jan 2010

Post Fri May 04, 2012 9:03 am

Just_a_fan wrote:
hardingfv32 wrote:Why bother with with the end plate above the main element? Is it requiered by the rules?

Why doesn't the end plate seal the bottom of the second element/flap? I though that an end plate on the low pressure side of a wing was always a benefit.

Brian

The endplates increase the downforce produced by the wing by effectively fooling the system in to thinking the wing is longer than it is. This is because the inevitable vortex produced at the wing tip reduce the downforce of the wing. It, in effect, makes the wing behave as if it were a shorter span. The endplates reverse this effect and so mean the wing produces more of its theoretical lift. We see these on airliners too in the form of vertical wingtips.

Unfortunately, the whole rear wing system still produces a big vortex at each end which creates big drag. So the teams use the louvres and the cut out behind the flap to reduce these large vortices. This will reduce the downforce but it improves the overall efficiency of the system. It's about efficiency. A more efficient system gives the teams more options.

This is what Brian was referring to re the low pressure side of the wing though. The typical method of destroying the vortex is to put a vertical segment *on the low pressure side*. Hence why airliners have wing tips that point upwards.
beelsebob
 
Joined: 23 Mar 2011
Location: Cupertino, California

Post Fri May 04, 2012 10:50 am

I think the idea here is to introduce flow that is contrary to the expected vortex direction hence the cut out's shape. As there is a low pressure area behind the wing between the endplates, the the flow will want to vortex one direction behind the flap and the other direction rolling off the ednplate. The shape of the cut out will determine how that forms.

I'm guessing that the sum of the drag from the two vortices formed this way is less than the drag from one big vortex and so is considered preferential.

Don't forget that the louvres in front of the flap in the endplate will allow some high pressure bleed outwards which will reduce the pressure differential at the end of the flap. This will also reduce the resultant vortex and so improve efficiency.

That's how I see it anyway, for what it's worth.
Just_a_fan
 
Joined: 31 Jan 2010

Post Fri May 04, 2012 2:17 pm

Might actually have been posted previously, but watch the two videos below for illustration purposes:
No modification of wingtip vortex - go to 5mins 11s.

Reducing effect of spillover via winglet
JMN
 
Joined: 29 Aug 2010

Post Fri May 04, 2012 3:21 pm

i saw the video and i think McLaren also must have the effect of spillover.
But i can't believe that McLaren makes RWs with vortices, because there is no downforce but drag. But we sometimes saw a vortex at the McLaren RW. So why they do this?

i mean we ofthen saw things like this: http://scarbsf1.files.wordpress.com/201 ... tices1.jpg
McMrocks
 
Joined: 14 Apr 2012

Post Fri May 04, 2012 3:46 pm

The vortices from the RW on the MP4-26 was noticably more visible due to the larger flap. It's all in the article related to the picture you posted, including how the current aspect ratio of the RWs simply doesn't make it feasible and much less optimal to mitigate the vortices to a point where they are hidden from the naked eye.
JMN
 
Joined: 29 Aug 2010

Post Fri May 04, 2012 5:31 pm

Just_a_fan wrote:That's how I see it anyway, for what it's worth.


What you propose does make sense.

The louver designs sure have been progressing over the last couple of years. I wonder why it takes so long to max out such a theme?

Brian
hardingfv32
 
Joined: 3 Apr 2011

Post Fri May 04, 2012 5:40 pm

McMrocks wrote:i saw the video and i think McLaren also must have the effect of spillover.
But i can't believe that McLaren makes RWs with vortices, because there is no downforce but drag. But we sometimes saw a vortex at the McLaren RW. So why they do this?

i mean we ofthen saw things like this: http://scarbsf1.files.wordpress.com/201 ... tices1.jpg



You cant make a RW without vortices, so how do you propose they would make one without them?
Huntresa
 
Joined: 3 Dec 2011

Post Fri May 04, 2012 7:19 pm

McMrocks wrote:i saw the video and i think McLaren also must have the effect of spillover.
But i can't believe that McLaren makes RWs with vortices, because there is no downforce but drag. But we sometimes saw a vortex at the McLaren RW. So why they do this?

All of the cars make rear wing vortices. It's a natural result of using a wing. Even wings with endplates make vortices. I've got some poor pictures of cars other than McLarens making rear wing vortices at Silverstone last year.

The important thing is to make the L/D as good as possible. Having 100kg more downforce is no good if it comes with 100kg of drag, for example, because you'd get destroyed on any long straight. Getting 75kg more downforce but with only 25kg extra drag, on the other hand, is worth it. Sure you'd be marginally slower on to the straight from the corner (assuming the corner exit speed is downforce limited) but you'd be quicker for most of the straight (think China's long straight here as a good example).

Don't forget that powered absorbed by drag is a cubic relationship with respect to velocity ( bhp absorbed = (Cd . A . v^3)/1225 ) so anything you can do to reduce drag at high speed is good - the teams can't get any more power from the engines so they have to concentrate on drag in order to get decent straight line speed. After all, this is what the DRS is all about - letting the teams dump a good chunk of drag.
Just_a_fan
 
Joined: 31 Jan 2010

Post Fri May 04, 2012 7:21 pm

hardingfv32 wrote:The louver designs sure have been progressing over the last couple of years. I wonder why it takes so long to max out such a theme?

Brian

Presumably the louvre designs change to match changes elsewhere in the package. Change the front wing and you will alter the flow getting to the rear wing so you'd need to adjust accordingly, for example.
Just_a_fan
 
Joined: 31 Jan 2010

Post Fri May 04, 2012 8:52 pm

McMrocks wrote:i saw the video and i think McLaren also must have the effect of spillover.
But i can't believe that McLaren makes RWs with vortices, because there is no downforce but drag. But we sometimes saw a vortex at the McLaren RW. So why they do this?

i mean we ofthen saw things like this: http://scarbsf1.files.wordpress.com/201 ... tices1.jpg


You see, McMrocks, they don't choose to make the vortices. the vortices is a physical phenomena that happen at the corner of the wing where you have a high pressure gradient and a tripping surface. It is all a consequence. Vortices in this area make drag so team try to reduce them, by making fancy gills and vertical gurney flaps on the side of the RW end plates.
"You can't change what happened. But you can still change what will happen.
Sebastian Vettel"
PlatinumZealot
 
Joined: 12 Jun 2008

Post Sat May 05, 2012 9:32 am

JMN wrote:Might actually have been posted previously, but watch the two videos below for illustration purposes:
No modification of wingtip vortex - go to 5mins 11s.

Reducing effect of spillover via winglet


Question: why if the problem is air comming from beneith the wing, does the winglet tries to cut off the top and not the bottom?
I understand how the "current" solution works, but it seems more logical to tackle the bottom.

Sorry for the off-topic
I think overtaking is an art - Montoya
AnthonyG
 
Joined: 3 Mar 2012

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