Gaz. wrote:Dipesh1995 wrote:I would say that the large undercut is trying to get as much air as possible to rear of the car. The larger the undercut, the less likely air flow could leak from the top of the floor to underneath it and disturbing the flow underneath the car. Also, the larger and tighter the undercut, the faster the velocity of the air is around the sidepods as a stronger low pressure region is created around them and towards the coke bottle area thus increasing the velocity of the air which would then flow on top of the diffuser increasing downforce. Obviously if the sidepod undercut is too aggressive, then there is chance the air flow will stall so there is a balance of increasing the velocity of the airflow around the sidepods and towards the coke bottle without stalling it.
So I presume this undercut wouldn't work properly with those large wishbone fairings? I'm not an aero man at all, but the wishbones appear to be counter productive to what you've just said- to this layman anyway
There seems to be some confusion about those wishbones. At first glance all they seem to do block the airflow hence why many have called them blockers. I would say the term "blocker" is actually a misnomer. Think about it this way, if a car is moving through the air, the air is GOING to flow around it somehow. So on the McLaren there is the air flowing toward the back of the car along the floor. The air then hits the suspension mushrooms (what has been termed as blockers). The airflow has to go somewhere. It can't go straight through obviously except in the small gaps. It can't go underneath as the diffuser roof is there. It only really has one direction to go, upwards at an angle. Therefore behind the suspension mushrooms will be a low pressure zone that increases the pressure differential in the diffuser and hence pulls more air through it increasing downforce.
Now onto the whole undercut thing. Remember that, like everything else in Formula 1, undercut comes with a compromise. The more undercut you have, the higher up all the pieces in the sidepods will be increasing the centre of gravity. The sidepods are more complicated than most think and one place where the aero guys have to work hand in hand with the cooling guys. The cooling guys know how much cooling they need and therefore the size of radiators and airflow figures that these radiators need. The aero guys then have to take these radiators and figure out how exactly to lay them to figure out car exterior aerodynamics traits, car internal aero and and packaging (C of G) constraints.
Why the undercut you say? Well think of it this way. Starting from the front of the T-tray, above the floor, what is the shortest and fastest point to get airflow to the top of the diffuser? It is along the floor. The more you put in the way on the floor the more the airflow has to go around and divert its flow. It should then hold true that the larger you have an undercut the less there is in the way of the airflow restriction to the rear of the car. Now you throw in the shape of that car. From a purely minimising drag way of thinking the most ideal shape would be something along the lines of a constant radius turn with the largest radius (think of it as a smaller angle change over a larger distance) possible. It is the shape that provides the most gradual pressure gradient. It also has the greatest chance of keeping the flow laminar however laminar flow is a whole other kettle of fish.
The lower the pressure gradient the lower the drag. Of course all my explanations were extremely simplified but I hope it helps people somewhat. Just remember that more isn't always better and, especially with sidepods, everything is a compromise, no more so than the whole undercut issue.
P.s. To the mods, I answered here but I feel as if the last few posts about undercut should be in their own respective thread.