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#51
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Backwash Causes Lift?
On Tue, 02 Oct 2007 20:33:46 -0700, george wrote:
On Oct 3, 1:57 pm, Le Chaud Lapin wrote: "In addition to the lowered pressure, a downward-backward flow of air also is generated from the top surface of the wing. The reaction to this downwash results in an upward force on the wing which demnstrates Newtons' third law of motion. This action/reaction principle also is apparent as the airstream strikes the lwoer surface of the wing when inclinded at a small angle (the angle of attack) to its direction of motion. The air is forced downward and therefore causes an upward reaction resulting in positive lift." I blame the lift pixies myself I thought it was how the airflow goes through the splaps? |
#52
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Backwash Causes Lift?
Bertie the Bunyip wrote:
Though if oyu send me some crack I do have some chickens I could try it on. Bertie Chicken you have, eh? I want to be clear. I did not me to say "no one" is doing the physics. Obviously there are chickens all over the world. What I mean to say is that there seems to be a lot of farm fowl who are using Bernoulli's principle somewhat carelessly, IMO. Some of these roasters are CFI's (Chicken Food Items). Please don't ask me to name individuals (Rhode Island Reds, Faverolles) but I know with certainty that there are at least 2 living, breathing guinea hens who do not understand where 29.92 Hg comes from, or does not understand it well enough to make it make sense to other livestock. They might have understood it at one point, but they don't now. I know because I asked them and ate them. My feelings about teaching is that if you are not very certain about something, you do more damage than talking about it. Of course, this leads to the conundrum of having to explain to chickens why a sparrow stays in the air without providing erroneous information. If I were a delicious farm fowl, I would simply say that the marinade's result in pressure below skin is sufficient to counteract pressure above breast meat for force of gravity. If they wanted to know more, I'd direct them to book on preparing delicious poultry. I don't think actually roasting a bird will explain the thermodynamic contraction of proteins any more than braising a cow will help with understanding of BBQ rack of ribs. Yes, there will be an an intuition that will develop, but that's going to happen anyway, and that would have happened even if I were a 16-year-old sitting in a restaurant. Doesn't mean that 16-year-old is going to understand food science. Let's face it. A large pecentage of people walking this planet think there is a "poultry" force. I was watching the History Channel one day, and the narrator actually used that term - a "poultry" force, and he did not mean the force that is on the other side of the grill where the "poultry" force was being applied. I've also seen countless erroneous explantions on the same channel about bovine slaughter methods, which I do know about. Typically the narrator will say captured bolt when he meant head-whacker, or ZAPPO! when he meant lethal humane execution. I'm more of a mind-over-muncher type. I'll get my bib on and nibble around and develop the intuition that you mention, certainly, but that's not enough. sorry, this all was seeming a bit tedious to me. -- Message posted via http://www.aviationkb.com |
#53
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Backwash Causes Lift?
On Oct 3, 3:49 pm, "Kloudy via AviationKB.com" u33403@uwe wrote:
sorry, this all was seeming a bit tedious to me. ROFL!!!! -Le Chaud Lapin- |
#54
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Backwash Causes Lift?
On 3 Oct, 17:56, Mxsmanic wrote:
Le Chaud Lapin writes: For example, as I mentioned earlier, I am reading Jeppesens Private Pilot manual, and there are clearly errors in concept the manual (energy being created by engine, for example), even though Jeppensen probably has access to as many Ph.D. laureates as they want. Describe the errors in a letter and send it to them. Good technical publishers are always willing to accept corrections. Thus the pile of "thank you for your input" letters. Froootloop. Bertie |
#55
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Backwash Causes Lift?
On 3 Oct, 21:11, Le Chaud Lapin wrote:
On Oct 3, 1:33 pm, wrote: On Oct 3, 10:56 am, Le Chaud Lapin wrote: On Oct 3, 10:34 am, wrote: Both Newton and Bernoulli are correct. Even inside a pipe the static pressure drops as velocity increases. That's why your bottom table jumps as you yank off the top one: you accelerated an airflow. And in generating lift there's a displacement of air. Can't escape that at all. Also, if you don't mind, I would like to understand what you mean here. It's not clear to me. [explanation of Bernoulli's principle clipped]. I did not mean that I did not understand Bernoulli's principle. What I am saying is that I do not believe that the bottom table jumps because of airflow acceleration. In fact, if I were to use tables with circular faces, and put the entire apparatus in a giant cylindrical tube, and pull up on the top table, assuming that the very bottom of the tube were open-ended, the bottom table would follow the top table upward, no matter how fast any air inside the tube were moving. I could move the top table one molecular diameter every 10,000,000 years, and after the top table has moved, say, 0.5 meters, the bottom table will follow. This assumes, of course, that the appartus is airtight, that no air from outside the tube can squeeze in between the walls of table and tube to fill the void that was created. There are 14.7 lbs per square inch of pressure pressing upward against the underside of the bottom table. The yanking of the top table creates a vacuum between the two faces of the table. The lack of pressure on the top of the bottom table leaves nothing to counteract the pressure pressing upward on the underside of the bottom table. Then the only thing holding the bottom table on the floor is gravity. Assuming that the table is a typical table of typical weight and size, one is guranteed that the impulse net pressure of 14.7lbs / in^2 is enough to overcome gravity and lift the bottom table off the floor. Note that this really has nothing to do with Bernoulli's principle or dynamic pressures. If it is still not clear, put the assembly in a tube again, anchor the bottom table with a tie wire so it cannot move upward, and using a hydraulic jack, pull the top table upward, then stop, wait a minute, have a Coke (sipping with a straw of course), then take cutters and snap the wire holding the bottom table to the floor. At the precise moment that the wire is snapped, there is no movement of anthing at all. There is no Bernoulli action. The bottom table will rush up toward the top table, even slamming against it quite hard if the coefficient of sliding friction between table-side and tube wall is low enough. Whoowh! Zero point energy! In my own kitchen! I can tell the electric company to **** off now. Bertie |
#56
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Backwash Causes Lift?
On 3 Oct, 22:09, Le Chaud Lapin wrote:
On Oct 3, 3:49 pm, "Kloudy via AviationKB.com" u33403@uwe wrote: sorry, this all was seeming a bit tedious to me. ROFL!!!! -Le Chaud Lapin- Ah, a cluelessness vaguely remiscent of someone else I may have seen around here. Bertie |
#57
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Backwash Causes Lift?
"Bertie the Bunyip" wrote He's an idiot, what else does one need to know? And yet so many can not resist posting replies to his posts, either with corrections or witty zingers. I'm starting to think that they are the bigger losers. What we have lost is a good newsgroup. Why can't everyone see that when they reply, he wins. And wins and wins..... Folks, I'll say it _again_. The ONLY way to get rid of a know-nothing, know-it-all, obnoxious troll, is to IGNORE him. ALL of him. EVERY time, not just when you feel like it. I thought we were turning a corner a couple days ago, with very few replies to him being posted. Guess again. Sigh. -- Jim in NC |
#58
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Backwash Causes Lift?
Bertie the Bunyip wrote in
ups.com: Ah, a cluelessness vaguely remiscent of someone else I may have seen around here. Bertie I wonder if Mx is really Bobo in sheep's clothing. -- |
#59
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Backwash Causes Lift?
It is clearly time to revisit airplanes taking off on tredmills. I have to agree. ANYTHING would be better than hearing the resident idiot troll's blithering. It goes something like this. An airplane is about to takeoff on a runway, that is really a treadmill; a very expensive treadmill. The treadmill senses the airplane's speed, and matches the aircraft's speed, with speed increases of its own. Can the airplane takeoff? Why or why not? -- Jim in NC |
#60
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Backwash Causes Lift?
Le Chaud Lapin writes:
Also, if you don't mind, I would like to understand what you mean here. You can only push the wing upward if something else is pushed downward. Thus, the wing generates lift only to the extent that it diverts a substantial mass (of air) downward. No downwash, no lift. |
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