#1
Hey there, an aerodynamics/lift/drag/downforce question for anyone out there knowledgeable about such things

I'm currently researching the mechanics of an F1 car and of course, aerodynamics are hugely important for creating that downforce; and alot of the materials i've found have used Bernoulli's equation for explaining it (where faster fluids give lower pressure and so cause an imbalance etc)

But my physics teacher has been quite animated about how it is useless practically as it says that the particles of air must meet back up together after transversing each side of the aerofoil; when in reality they do not and it's to do with Newton's 3rd law

Is the a particular angle i should take on this? Such as mention Bernoulli's but point out the flaw or is there another idea out there that can be discussed?
#2
i believe it uses the same principle as airplane wings , but upside down , and airplanes do fly (a pratical use of bernoulli's equation) . i think you're right and your teacher doesnt know what he's talking about
#4
Quote by Woozye
i believe it uses the same principle as airplane wings , but upside down , and airplanes do fly (a pratical use of bernoulli's equation) . i think you're right and your teacher doesnt know what he's talking about


Haha well I was going for the angle that my teacher was right, as if bernoulli's is 100% true planes can't fly upside down, otherwise they'd just be sucked downwards, and so it has more to do with Newton's laws where they air being forced down pushed the plane up, and to fly upside all you need to do is get at an angle enough to do the reverse. But aye if anyone's researched this as part of a course or anything and has any tips for looking into it, i'd be grateful
#5
Bernoulli's equation, insofar as I know, does not require that particles on each side of a body that start at the front must meet at the back at the same time.

BE is an approximation made for incompressible flow. Meaning, we ignore the fact that the density of air changes with speed, which simplifies things quite a bit. You can assume incompressible flow conditions when the Mach number is less than 0.3, which is a commonly-used standard. There is nothing special about M=0.3; it's just a standard. Since most cars do not break the M=0.3 boundary, incompressible flow is a safe assumption to make.

However... those who design cars like the F1, or solar cars, or anything really expensive, use Computational Fluid Dynamics (CFD) analysis on a computer. Takes a few days to run the simulation for a very simple setup. But you can optimize designs with many CFD packages.

Keep in mind that BE is not a very useful computational tool. Cars see a lot of flow separation in their wakes, and this requires turbulent flow and viscous flow analysis.

EDIT: Another way to state BE is to say that total pressure is constant along a streamline. This changes, as well, by more than ~5% with M>0.3. With supersonic flow, the total pressure will change because of non-isentropic processes occurring in the shock waves.

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