checkered wrote: I'm not entirely clear on whether the level of the energy or the span of the "disturbance" are the main "problems" currently - there could also be something else to the predictability, method of decay and distribution of the turbulent wake - something more easily managed by less aggressive shapes than todays'.
Let's try to separate the sources of problem:
Upwash:
-The upwash actually decreases the angle of attack of the front wing so it decreases downforce, the problem is a direction problem (conditionned by the steep angle of the diffuser, but also the gradient of pressure from diffuser to rear wing).
-The upwash impacts the front wing directly increasing pressure on the front wing, the magnitude is then proportionnal to velocity of the upwash and mass in the upwash. The velocity depends on the diffuser vortex decay rate and diffuser area-downstream gradient of pressure (if the zone behind the diffuser is low pressure, the upwash willbe stronger) this is dependent on the turbulence inside the diffuser and the coupling from the rear wing. The mass is of course dependent on the mass recovered by the diffuser.
-The upwash decreases the velocity over the front wing by having more vertical component velocity. Cause are same that above.
-The upwash by impacting the front wing creates marginal vortices at the tips of front wing, increasing drag. The magnitude of those are dependent on the upwash strength but also the upper side of the front wing pressure repartition.
In any case, the shorter the front wing, the greater the drag.
-The upwash expands when slowing down,eventually forming turbulence, The higher the front wing, the more it is in the larger upwash zone. The zone is dependent on the coupling with rear wing, the mass ejected by the diffuser, the slowing down rate of upwash.
The rear wing:
-the rear wing naturally creates a wake of recirculation (the kutta condition).
The strength of recirculation (then turbulence) is dependent on the pressure difference between lower and upper side of the rear wing that is, the pressure drag of the wing or the Cl (the more the Cl for a given profile, the more the pressure drag, thus the more the turbulence).
This recirculation decreases the velocity over the front wing of the following car, thus lowering the total forces.
The recirculation in itself creates a low pressure zone further decreasing total forces.
This is here than the slipstream compromise has to be done.
-the rear wing created tips vortex; Their behavior is very variable, they can go upward or downward.
when a downwash is created the downwash increases the front wing angle of attack increasing briefly downforce before increasing the angle of attack outside the max AOA, thus stalling the wing.
Note that considering the direction of those vortices, this is can affect either the front wing or the rear wing (or any wing inbetween) and is really dependent on geometry.
-The rear wing/diffuser coupling extends the turbulence of the rear wing by creating an adverse pressure gradient downstream of the rear wing, the decay of turbulence being then entertained.
Those vortex mix with the marginal vortex and can impact the front wing either by increasing the angle of attack of thisone or by inducing turbulent flow transition on the front wing.
Decreasing coupling increase the decay rate of turbulence.
Vortex generators:
-Vortex generators create cascade vortex whose decay will depend on gradient of pressure encountered along the downstream of the car and in case bargeboard and diffuser will depend also on decay of primary vortices.
When vortex slow down they grow. Front wing impacted see depending on the rotation of vortex creation of induced drag but also early turbulent transition leading to thickening of the boundary layer, lowering the camber of the wing,thus lowering downforce.
-Vortex generators can generate downwash or upwash, depending on their placement they can impact the front wing.
-The scale of vortices is dependent on pressure distribution in the vortex, the lower the pressure at the center (which suggest high wingtip vortex, or great adverse pressure gradient) the greater the scale of the vortex.
The mix:
-The scale of marginal vortices, the strength of upwash and coupling will define the width, lenght and height of turbulences.
The center part of the front wing is the one that suffer the most from combined effects.
Narrowing rear wing, decreasing coupling, banning vortex generators (inside diffuser too) and limiting mass flow inside the diffuser will lesser the dimensions of the wake.
My take on that is that we should mainly focus on having not interfering flow fields rather than limiting too much the aeros.
But it is inevitable as racing is dynamic.
I think the steeper diffuser (but higher) is too simplify the shape and allow less flow rate inside it (by forcing the increase of the entry of the diffuser).
But for me the coupling decrease and front wing lowering (and widening) is already sufficient.
AeroGT3, i'd really like your works. The rear tyres AFAIK won't be bigger next year.
