seagull
Well-Known Member
In reference to my previous post, I ended up not having time last night to write much. I only have a couple of minutes now, but thought I'd get the ball rolling here.
First, there is NO "Bernoulli vs Newton" debate. Period. They are not competing theories. There is one very particular aspect that might be construed as "competing" (but it's not, really), and that is "impact lift" which is only a factor at extremely high altitudes and mach numbers, where the effect of high velocity air hitting the bottom of the wing starts to be significant compared to more conventional lift, due to the extremely thin air and very high kinetic energy of the air molecules.
Second, there is no truth to the notion that air molecules that go over the top of the wing reach trailing edge at the same time as air that goes underneath the wing. In fact, the air that goes over the top of the wing actually will generally reach the trailing edge BEFORE the air that goes under it!
This whole notion that the air that is deflected downwards creates an equal and opposite reaction that pushes the wing upwards is a misunderstanding of Newton's laws. It is similar to people saying that the air rushing out of a balloon is creating an equal an opposite reaction so the balloon moves. No, the balloon moves because it is pushed! The truth is that the place where the opening is on the balloon is the only area that is NOT pushing, so the balloon moves the opposite direction.
I think some of the confusion comes from the fact that all of the Bernoulli equations are derived from Newton's laws. Really just extrapolations of them.
I am out of time at the moment, but the next thing to consider is a discussion of potential and kinetic energy, and how that relates to a fluid and the terms used for a fluid vs. a solid object. We will then look at rotational flow and finally how to achieve that flow.
First, there is NO "Bernoulli vs Newton" debate. Period. They are not competing theories. There is one very particular aspect that might be construed as "competing" (but it's not, really), and that is "impact lift" which is only a factor at extremely high altitudes and mach numbers, where the effect of high velocity air hitting the bottom of the wing starts to be significant compared to more conventional lift, due to the extremely thin air and very high kinetic energy of the air molecules.
Second, there is no truth to the notion that air molecules that go over the top of the wing reach trailing edge at the same time as air that goes underneath the wing. In fact, the air that goes over the top of the wing actually will generally reach the trailing edge BEFORE the air that goes under it!
This whole notion that the air that is deflected downwards creates an equal and opposite reaction that pushes the wing upwards is a misunderstanding of Newton's laws. It is similar to people saying that the air rushing out of a balloon is creating an equal an opposite reaction so the balloon moves. No, the balloon moves because it is pushed! The truth is that the place where the opening is on the balloon is the only area that is NOT pushing, so the balloon moves the opposite direction.
I think some of the confusion comes from the fact that all of the Bernoulli equations are derived from Newton's laws. Really just extrapolations of them.
I am out of time at the moment, but the next thing to consider is a discussion of potential and kinetic energy, and how that relates to a fluid and the terms used for a fluid vs. a solid object. We will then look at rotational flow and finally how to achieve that flow.