Originally Posted by BrokenVert
But anyway this models the way that air moves around the body. See the very sudden dusplacement of the streamlines right at the step? And how they suddenly change thickness in several places and just generally look confused?
That is one of the mechanisms that creates drag, this change in the location and thickness of streamlines. And this model only shows one type of drag, it doesnt even account for things like surface friction or turbulence, which the step creates both.
however below you can see the smooth airflow that in effect goes under the car. This is a nice flow and as many have said this is what they were going for.
I unfortunately dont have the time to do anything better than this, but it gives an idea as to why the designers did what they did.
Graph was easy to see what you were trying to say. Thumbs up for the effort. Upon inspecting the step part of the nose a bit further, I'm just a bit more convinced that they probably managed efficient Cd. CFD experts from Lotus say higher body work in front of the car in F1 generally contributes to better downforce. Managing correct frontal pressure is possibly one of the most important aspect of a racing car. Martin from McLaren even admitted stepped nose has aerodynamic advantage.
Looking at the step nose, I don't see much of turbulence nor disadvantage of air flow. At the point of "impact", where the step occurs, it actually creates downforce due to brief higher pressure, while smooth surface in front and rear of the impact area is lower in pressure. Air molecules will not stagnate in this case, at least not severe enough to cause problems. Most stepped nose I've seen in pictures have contour design that "soaks" and streams air down into middle towards the driver/intake. A good compromise I say. Now, if the "step" was angled like brick stairs, I could see some serious problem.
I guess what I'm trying to say is that amount of extra pressure build-up that most people worry about is offset by other variables that positively effects the aerodynamics. Curious to hear different analysis.