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Overtaking in 2017


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#1 thegforcemaybewithyou

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Posted 26 September 2016 - 09:15

As there has been a bit of discussion in the Mercedes thread ( http://forums.autosp...-hybrid/page-36 ) about wake turbulence and overtaking and how it could evolve with next year's cars, i thought there should be a new thread.
 
I want to do some simple spreadsheet calculations on how the gap between two cars changes on a straight, both for 2016 and 2017. So before i start, i want to discuss the parameters to consider.
 
What do you think about the assumed data?
 
2016
power: 850 hp (rear wheel power in the race)
mass: 750 kg (mid race)
 
clA: 4*cdA (coefficient of lift cl * frontal area A)
crr: 0,015 (coefficient of rolling resistance)
vmax: 350 km/h
-> cdA 1,05 m² (coefficient of drag cd * frontal area A)
 
DRS effect: 10% drag reduction
 
 
2017
power: 875 hp (up a bit from 2016)
mass: 770 kg (increased min weight)
 
cdA: 1,15 m² (~+5%)
clA: 4*cdA
crr: 0,165 (wider tyres)
vmax: < 350 km/h
 
DRS effect: the same 10%. The rear wing will be wider but the the total drag will also rise
 
 
2016 and 2017
Drafting effect: d is the distance between the front wings of the two cars
 
drag factor drafting for trailing car:
d<6m -> 1
d>=6m -> 0,02813*ln(d) + 0,85
d>200m -> 1

drag factor drafting for leading car:
d<6m -> 1
d>=6m -> 0,002813*ln(d) + 0,985
d>200m -> 1 
 
 
With these assumptions you could then place two cars on the track, assume a gap (2, 5 or 10 tenths) and see how much track length is needed for the car behind to catch up in different configurations.

Edited by thegforcemaybewithyou, 03 October 2016 - 20:30.


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#2 Charlieman

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Posted 26 September 2016 - 11:57

cdA -- coefficient of frontal area?

 

clA -- body form drag, assuming it is four times frontal area?

 

crr -- something to do with tyre width? Rolling resistance?

 

Rolling resistance is not proportional to tyre width. It's a factor of tyre pressure, width, aerodynamic and mechanical loads, stickiness and the things I've forgotten to mention.



#3 thegforcemaybewithyou

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Posted 26 September 2016 - 12:44

Sorry, added some annotations and units in the first post.

 

cdA = cd*A = coefficient of drag * frontal area

clA = cl*A = coefficient of lift * frontal area (or downforce as we speak about race cars, should be in the region of 4 to 5 times the drag)

crr = coefficient of rolling resistance

 

I know there are a lot of factors that influcence rolling resistance, width being one of those. I assume it is very likely it'll increase with the wider tyres next year. 5% or 10%, what do you think? This however isn't a big factor in this calculation, aero drag is the most important to get right.

 

 

The drafting effect in reality should also be affected by the speed of the leading car. At zero km/h there is no draft zone behind the car, at 300km/h it should be larger than at 150 km/h. Any suggestions to modify the equation or does it seem not needed for this sim?

 

Any suggestions are welcome, as long as you translate them into math!



#4 Charlieman

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Posted 26 September 2016 - 14:21

When considering aero factors -- and I'd rather think about others -- tyre dimensions are very important. The team that works out how to optimally use wider tyres, front wings and resultant air flows will do well in 2017.

 

Slip streaming benefits both cars; the one in front goes faster too.

 

If we were to create F1 rules to make races better, we'd make cars smaller (new tyre regs make them wider) and lighter (hybrid technology is creating lighter batteries). We'd make cars that did not require an arcane starting procedure (lift the exhaust valve to starting position; check that the magneto is clean; ****** the ignition control on the steering column; pump prime the carburettor). When we drove 1970s cars that required a manual choke, we understood that a hot engine might be tricky to start. You'd think that F1 engineers are working stuff out from scratch.

 

A 2017 F1 car should start on the button on the grid. If it doesn't start, push it to the pits.



#5 Ross Stonefeld

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Posted 26 September 2016 - 15:30

I don't see how that deals with the issues of massive aero-induced understeer and/or non-existent braking zones. 



#6 Charlieman

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Posted 26 September 2016 - 15:45

I don't see how that deals with the issues of massive aero-induced understeer and/or non-existent braking zones. 

Underteer, Ross? When those F1 cars get going, they are a handful to control. There have been many recent races when the car went sideways owing to driver pressure on the loud pedal.



#7 Ross Stonefeld

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Posted 26 September 2016 - 18:05

That's great? But they still can't get close enough to pass. Downforce at the levels they run is not good for racing. 



#8 thegforcemaybewithyou

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Posted 27 September 2016 - 17:58

Slip streaming benefits both cars; the one in front goes faster too.

 

Jep, I'll consider a small benefit for the leading car, similar to the drafting factor.

 

For 2017, i now think that a ~10% in increase for cdA to 1,15 m² is more realistic than the 1,1 m² i assumed in the first post.

 

Any other suggestions or wishes? More buttons or less?



#9 thegforcemaybewithyou

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Posted 03 October 2016 - 20:44

With the data from the first post i first had a look what the effect of DRS is. As you can see, it is huuge.

 

The cars were set at a gap of 0,5s or a bit more than 25m front wing to front wing. The velocity of the trailing car is 170km/h at t=0s, the leading car of course starts with a higher speed as it could accelerate earlier. The gap then increases until the lines d v cross the vertical axis, then the gap comes down due to the drafting. DRS increases the speed difference and lets the car behind catch up much faster. When the trailing car has to leave the draft zone at d=6m the velocities for the Non DRS cars approach each other and the gap stays the same. The DRS car however keeps a speed advantage and continues to increase the gap. In reality the car that wa leading at the beginning would now benfit from the draft, but i didn't consider this.

 

BWPtUdX.png



#10 thegforcemaybewithyou

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Posted 03 October 2016 - 20:55

And a graph of the DRS effect in 2016 and 2017 with different assumptions, only showing the distance between the two cars.

 

The blue line shows the 2016 cars at 0,5s and 170km/h initial velocity for the car behind, it is very close to the yellow line for 2017 (0,5s gap, 170km/h). As following through corners will probably harder in 2017 due to more downforce, i increased the gap to 0,6s for the black line. The time and distance needed to catch the leading car increases and even if i consider the likely higher corner exit speed for the red line (0,6s gap, 190km/h) it is worse than in 2016.

 

Be aware it all depends on the assumptions i made!

 

Z3xEuSP.png