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Alan Baker wrote:
In article , Beryl wrote: Alan Baker wrote: In article , Beryl wrote: Alan Baker wrote: Beryl wrote: Alan Baker wrote: Beryl wrote: Alan Baker wrote: Beryl wrote: Alan Baker wrote: It's like the downwash argument. You can say "IT DOESN'T MATTER", when people argue that the air behind an aircraft is not deflected downward, but it *does* matter. Having an accurate understanding of the physical processes of flight matters. It isn't really deflected downward, not for long anyway. It's churning in a torus. Like a smoke ring. No. It really *is* deflected downward. The edges of the deflected area churn, and the air that is deflected ends up getting diffused among all the other air below *it*, but it really is deflected downward. And eventually, that downward deflection makes it way until it -- very diffusely -- impacts upon the surface of the earth. That is the only thing that finally stops it. After more than 100 years of flight, the atmosphere still hasn't been pushed down to the earth's surface. Sorry, Beryl, but you're just wrong. As I said, the atmosphere isn't getting any shorter. Do you disagree with that? Repeating that "the net flow is downward" isn't making progress. The net flow is downward until it hits the ground and the momentum is transfer to the earth. Has to be an equal upward flow. Somewhere. Where? Imagine riding in a C-130 Hercules. You're flying an RC model airplane in the cabin! (That's why I picked a C-130) The model's weight is applied to the cabin floor, of course, but the "downwash" from the model's wing doesn't pile up on the floor. http://www.efluids.com/efluids/galle...s/Morris_4.jsp The column of downward flow in the center doesn't really flow down so far, does it? Yes, it does. All the way to the ground. Spread out among lots and lots of air, but that's where the momentum *has* to go. Say where the _air_ has to go. The aircraft starts the air moving downward. Net downward momentum. The ground stops that net downward motion. What if there were no ground? Jupiter has atmosphere, gravity, and I don't see why a solid surface below is required for flight. |
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