FRONT WING & Y-250 VORTEX
The front wing plays the most important role in getting the car to have front end grip. This is important for reducing understeer and improving responsiveness. F1 drivers want to attack corners as fast as possible and a good front wing is crucial to achieve that. The front wing also balances out the downforce produced by the rear wing allowing suitable distribution between the front and rear axles.
To get technical the aero lift force equation is F = 0.5 × ρ × CL.A × v^2 , where CL.A is the coefficient of lift (negative as we are producing downforce) multiplied by the frontal area. ρ is the density of air and v is the air velocity. For and F1 car CL.A value is around the -4.0 - -4.5 region which gives the downforce produced by the front wing at 100 mph as around 168 kg. As downforce increases with the square of speed, at 200 mph the front wing on its own produces a huge 672 kg!
The front wing sits close to the ground as more downforce is created in 'ground effect' than in freestream. See here to understand more about ground effect. However, engineers cannot put the front wing too close to the ground as the airflow can separate from the wing's surface and stall which ends up producing even less downforce. A reason for this is that the gap between the wing and the floor can become small enough that viscous effects start to create blockage and flow is throttled.
In general, a front wing's downforce is directly proportional to its dimensions. Often restricted by regulations i.e. the current max width is 2000 mm. Front wings are also reciprocal too, different designs affect everything else downstream e..g the wheels, floor/chassis. For example if the front wing span is increased then the chassis downforce also increases but the rear wing downforce decreases. An inverse relationship is common in aerodynamics.
Another decision aerodynamicists have to make is where they want the wash to go. The wash of the front wing relates to the direction taken by the air downstream of the wing, especially from the outer parts. Inwash pass inboard of the front wheels. See Ferrari. Outwash passes outboard of the wheels. The front wing endplates are shaped to direct the air around the tyres to stop it hitting the tyres creating a lot of messy turbulent wake.
Mercedes and Red Bull favour the outboarded wing and Ferrari the inboarded. Notice how Mercedes' wing tapers upwards towards the outer edges (outboarding) whereas the Ferrari tapers downwards (inboarding). There is no definitive 'right way' but each have their own advantages. The ouboarded wing has more surface area for more front downforce but is also harder to create a consistent wash around the front tyres. It is very important for the wash to go around the front wheels and away from the body in order to generate maximum downforce from the diffuser. The inboarded wing creates less downforce at the front but more at the rear as air can be controlled to reach the air intakes and rear wing.
Another general aspect of a front wing is that two 'tip' vortices are produced in response to the differential pressure above and below the wing (low pressure below, higher above). The upper vortex spills outwards over the top of the endplate and the other one spills inwards under the bottom of the endplate. See mercedes. Note how it's neat how the engineers managed to direct one of the vortices into the front brake ducts.
A largely talked about feature of the newer style of front wings is the y-250 vortex. This is a vortex triggered at the inner tips of the elements on the wing. 250 because these elements must be no less than 250 mm from the centreline in the y- direction (horizontal).
There is a sudden change in pressure from the neutral centre of the wing to the point where the wing is first shaped. the air hits the transition point creating a powerful vortex which affects pretty much everything behind the front wing. See the AlphaTauri below and the difference in the y-250 vortex of the Red Bull and Ferrari.
The first object the vortex meets on its way downstream is a 'cape' or 'j-vane'.
A 'cape' is a long flat piece of bodywork that is located just under the car's nose. Mercedes were the first team to implement the cape in 2017 (shown on the 2020 Renault R.S.20). Notably for their 2020 car, Adrian Newey has fitted the Red Bull RB16 with a cape, with Renault and Racing point also doing the same.
The other option is to use a 'j-vane' which is what Ferrari and Haas use. See Ferrari below. Both broadly fulfil the same purpose.
When the y250 vortex hits the ‘cape’ or ‘J-vane’ it produces another vortex but this time rotating in the opposite direction. This vortex travel under the floor and then interacts with the bargeboard area of the car. All the little components on the bargeboard create their own vortices that go under the car resulting in a huge low pressure area that produces a large amount of downforce. Crazy to think that this chain reaction started with the inner tips of the front wing!
The original y-250 vortex is spinning strongly and also interacts with all the bargeboard vortices created and makes them even stronger; therefore adding even more downforce. It makes sense then, that teams want to try and maximise the use of the y-250 vortex wherever possible by utilising capes or j-vanes.
Different design approaches to the front wing can change the strength of the vortices. For example, the inboarded Ferrari wing will exaggerate the pressure differences at the transition point, therefore creating a more powerful y-250 vortex. This is why even the ouboarded deign of the Mercedes and Red Bull have elements of inboarding at the transition point in order to generate a strong y-250 vortex.
Engineers also want to be able to control the vortex as much as possible, if it is too strong then it could interfere too much with the new vortex produced by the cape or j-vane going to the bargeboards. But if it is too weak then it won't make it there and will just be pulled under the floor.
The advantage of the j-vane is that, as it has a vertical surface, it is good for mitigating the effects of a cross-wind by straightening out the airflow and maintaining vortex position.
The advantage with a cape is that it can be positioned further forwards and therefore closer to the point where the y-250 vortex is produced. This means it can affect the vortex sooner and reduces its ability to drift away and move about.
If you were an engineer, which one would you recommend: the cape or j-vane?