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Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 13:51
by machin
LVDH wrote:I think the next large part you should work on is your rear wing.
Do you think Ric will be able to improve drag whilst maintaining downforce from changes to the wing? And what should he look for to see if his wing isn't performing well in the first place... A longitudinal stream line plot through the rear wing?
I was thinking the best bet might be to keep playing with the diffuser... that would hopefully bring a big increase in downforce (maybe with little change to drag)... that would then leave the car with the COP too far back... to correct that issue Ric could replace the current twin element rear wing with a single element wing... that would bring the COP back to where it needs to be and lose a load of drag in the process..
...Of course, that does presume that a further big efficiency gain can be found with the diffuser....
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 13:59
by RicME85
Regarding the rear wing, it is just the one that Chris put on the KVRC demo car, I havent found a need to work on a different profile....until now maybe.
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 14:03
by machin
From this view it doesn't look like there is much to improve to me...?
What do you think LVDH???
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 14:05
by graham.reeds
Looking for that 0.006 reduction in drag coefficient and lift coefficient?
Just scanned through
this paper on vortex generators.
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 14:30
by LVDH
Well in general I would say that a two element wing will not achieve the L/D levels a single element wing can achieve. Have you seen two element wing profiles on efficient airplanes? They only use multi element for high-lift-configurations.
Using two elements is mainly good as you can get too much higher levels of lift.
I will use the image to create that wing and test it against the one I have.
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 15:48
by LVDH
The image resolution is a bit too low and I cannot find that wing on the KVRC homepage. If you like you can send it and I can try and see what it does on my car.
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 16:58
by RicME85
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 19:42
by machin
LVDH wrote:Well in general I would say that a two element wing will not achieve the L/D levels a single element wing can achieve. Have you seen two element wing profiles on efficient airplanes? They only use multi element for high-lift-configurations.
Using two elements is mainly good as you can get too much higher levels of lift.
The main thing is to test the single element at an angle of attack which generates the same downforce as the current two element one in order to maintain the correct balance... Unless Ric takes wing off the front as well... But compared to others in the championship he is still a bit light on downforce... Which I still think is "hidden" in the diffuser/floor... But will be interesting to see the results of your test....
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 19:49
by LVDH
OK, numbers are in.
As I did not have that much time I will mostly just post the naked numbers for the complete car.
The simulations were carried out with the car I showed when I tried the open side pods.
So raising the front wing 20mm barley affects drag but reduces downforce by 4.7% and shifts CoP 12cm backwards.
Lowering the front wing by 20mm (illegal) creates 0.6% additional drag with 5.4% more downforce and moves the CoP again by 12cm but to the front.
The rear wing has a large effect. The two element wing creates 15% more drag with only 7.7% more downforce, shifts the CoP 14cm backwards and costs about 300 counts of L/D compared to my single element wing.
I also put the force distribution images from my race 5 entry beside some of the ones you posted:
On the downforce images on both cars you can see four distinct sections: front wing, suspension cover, diffuser and then rear wing. If you compare the diffuser section yours is comparable to mine. You rear wing is not though. On both cars the largest bar reaches about 800N but on mine the other two bars are larger. On the drag images your bars are larger than mine. So to me you have to improve that rear wing for the next large step in your development.
If we look at the first two sections, your front wing is creating more or similar levels of downforce my car does. It seems at the cost of drag though. You suspension cover could also use some work if you compare with my car.
Still, having the numbers from above in mind I have to say you need a better rear wing. Also I would say your rear wing deserves some nicer air flow to it as it seems that your rear wing does not produce as much downforce as it does on my car. This surprises my as your suspension cover seems to do exactly that.
What do the others think?
I think this small check clearly shows that your rear wing is the next thing to work on.
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 19:51
by machin
graham.reeds wrote:Looking for that 0.006 reduction in drag coefficient and lift coefficient?
Just scanned through
this paper on vortex generators.
Yeah, that is interesting... I don't know if you saw my post a few pages back but I found on a simple floor/diffuser model putting some vortex generators near the leading edge of the floor generated about 15% more downforce and a little reduction in drag (with other flow conditioners dotted around the model the eventual improvement was 49%!) so VG's can have big impacts on performance if sized/positioned correctly... Although I was reading an interesting aeronautics article that said "VG's are like hoovers; they clear up someone else's mess!" Which I thought was quite amusing!
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 20:00
by machin
LVDH wrote:OK, numbers are in.
As I did not have that much time I will mostly just post the naked numbers for the complete car.
The simulations were carried out with the car I showed when I tried the open side pods.
So raising the front wing 20mm barley affects drag but reduces downforce by 4.7% and shifts CoP 12cm backwards.
Lowering the front wing by 20mm (illegal) creates 0.6% additional drag with 5.4% more downforce and moves the CoP again by 12cm but to the front.
The rear wing has a large effect. The two element wing creates 15% more drag with only 7.7% more downforce, shifts the CoP 14cm backwards and costs about 300 counts of L/D compared to my single element wing.
I also put the force distribution images from my race 5 entry beside some of the ones you posted:
http://mantiumcae.com/wp-content/upload ... iumRay.png
On the downforce images on both cars you can see four distinct sections: front wing, suspension cover, diffuser and then rear wing. If you compare the diffuser section yours is comparable to mine. You rear wing is not though. On both cars the largest bar reaches about 800N but on mine the other two bars are larger. On the drag images your bars are larger than mine. So to me you have to improve that rear wing for the next large step in your development.
If we look at the first two sections, your front wing is creating more or similar levels of downforce my car does. It seems at the cost of drag though. You suspension cover could also use some work if you compare with my car.
Still, having the numbers from above in mind I have to say you need a better rear wing. Also I would say your rear wing deserves some nicer air flow to it as it seems that your rear wing does not produce as much downforce as it does on my car. This surprises my as your suspension cover seems to do exactly that.
What do the others think?
I think this small check clearly shows that your rear wing is the next thing to work on.
I tend to agree! From those examples it does indeed look like there isn't much wrong with Ric's diffuser!
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 20:08
by machin
One thing; Your front wing looks to have quite a long chord compared to Ric's... The large amount of up wash off Ric's front wing appears to be what creates the lift on the suspension cover.... So maybe it is actually also the front wing which needs to be looked at... Maybe two larger (longer chord) elements with less overall AoA are what is needed? Also Ric tried 3 different suspension covers earlier with negligible benefit...
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 20:30
by LVDH
Comparing the approach of a Variante Stlye front wing with my approach, to me it appears that in total they are similar. While "concept A" creates a lot of initial downforce, the air flow needs to be straightened with the suspension cover, which creates lift.
My "concept B" creates less downforce but it does not need the detrimental suspension cover.
A first look at the force distributions does not clearly favor one over the other.
And I know that designing the front end of the car is very complicated, esp. compared to designing a better rear wing. So this should be prio. 1!
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 20:56
by machin
Agreed...
Re: [KVRC ~ish] CCE LMP01
Posted: 05 Oct 2015, 21:02
by hollus
RicME85 wrote:
This would probably be a small improvement, although it might help extract a bit more air from the diffuser: Why does the rear of the car end with a surface perpendicular to the flow? That's always going to create drag for very little benefit (McLaren mushroom suspensions, anyone?).
Actually, Machin has already suggested a solution to that which doesn't make the expansion in the diffuser even more aggressive:
This might apply to the surface in front of the diffuser as well. Shouldn't all car edges be sharp from behind?
