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#81
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visualisation of the lift distribution over a wing
In article ,
brian whatcott wrote: Alan Baker wrote: /snip/ I have never noticed the fabric lifting on my wings, however I have seen the fuel siphon out of a wing tank due to an improperly applied fuel cap. And greater pressure in the tank than outside of it... Right, but in a sealed metal tank, is all that other fuel PUSHING the fuel out of the vent since air can't PULL it out? First of all, the tank is not completely sealed. If it were, the fuel pumps would soon have difficult pumping the fuel out of the tank. So, yes, the greater pressure inside the tank is pushing the fuel out. Hmmm...it probably goes more like this: there's a 100 mph? wind past an open port, with some venturi effect certainly, but plenty of turbulence. If you beat up the surface with a gusty blow, it gets wavelets which can lap the filler and blow out the fuel. Which reminds me of that trick that suction pumps use for high lift. As you probably know, if you pump down even to a vacuum above a tall 3water pipe, the water will not rise more than about 30 ft - (if it were mercury, it would not rise more than 29.92 inches on a standard day, remember?) Anyway, the mine engineers who want to pump up water MORE than 30 ft, say 40 ft without placing a force pump at the foot of the head, blow air into the water column which has the effect of reducing the density of the mix. If the relative density goes down from 1.0 to 0.5 they COULD pump up to nearer 60 ft. How bout that! Brian W How about it? It still doesn't change the physical reality that air doesn't *pull* on the wings. -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
#82
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visualisation of the lift distribution over a wing
Alan Baker wrote:
In article , Jim Logajan wrote: Any change in pressure is *by definition* a change in the number of particles in the fluid that are impacting the surface. That assertion is incorrect. You are no dummy so I'm sure you'll correct it when you realize the errors. Sorry, but it's not. Pressure is created by particle collisions. Hmmm...looks like Jim expected too much from you: the kinetic theory of gases has it that pressure may be computed from the temperature AND the density of gases... that is to say, by retaining the SAME molar quantity of gas, and raising its temperature (which translates to a higher velocity), the pressure is increased P.V = R.t and all that.... Put it another way: each "hotter" molecule reverses direction at a surface with greater force. Brian W |
#83
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visualisation of the lift distribution over a wing
Alan Baker wrote:
I have never noticed the fabric lifting on my wings, however I have seen the fuel siphon out of a wing tank due to an improperly applied fuel cap. And greater pressure in the tank than outside of it... /snip/ So, yes, the greater pressure inside the tank is pushing the fuel out. Hmmm...it probably goes more like this: there's a 100 mph? wind past an open port, with some venturi effect certainly, but plenty of turbulence. If you beat up the surface with a gusty blow, it gets wavelets which can lap the filler and blow out the fuel. How about it? It still doesn't change the physical reality that air doesn't *pull* on the wings. You're still singing the last hymn, Alan. We are now discussing how an open tank, with a 100 mph wind blowing over its top, can lose its fuel over the top. Do you think the tank has GREATER pressure due to the venturi effect of the airflow? Brian W |
#84
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visualisation of the lift distribution over a wing
In article ,
brian whatcott wrote: Alan Baker wrote: In article , Jim Logajan wrote: Any change in pressure is *by definition* a change in the number of particles in the fluid that are impacting the surface. That assertion is incorrect. You are no dummy so I'm sure you'll correct it when you realize the errors. Sorry, but it's not. Pressure is created by particle collisions. Hmmm...looks like Jim expected too much from you: the kinetic theory of gases has it that pressure may be computed from the temperature AND the density of gases... that is to say, by retaining the SAME molar quantity of gas, and raising its temperature (which translates to a higher velocity), the pressure is increased P.V = R.t and all that.... Put it another way: each "hotter" molecule reverses direction at a surface with greater force. Brian W I'm perfectly aware of that, but that hardly matters for the scope of our discussion of the effect of pressure on a wing. The point I'm making is that all else being equal, more collisions means higher pressure and fewer means lower pressure, but that pressure is therefore always a positive value that acts toward the surface to which it is applied. It is *never* acting away from that surface; i.e. "pulling". That is the only reason I mentioned a vacuum, because it is a situation in which there is *by definition* zero absolute pressure. -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
#85
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visualisation of the lift distribution over a wing
In article ,
brian whatcott wrote: Alan Baker wrote: I have never noticed the fabric lifting on my wings, however I have seen the fuel siphon out of a wing tank due to an improperly applied fuel cap. And greater pressure in the tank than outside of it... /snip/ So, yes, the greater pressure inside the tank is pushing the fuel out. Hmmm...it probably goes more like this: there's a 100 mph? wind past an open port, with some venturi effect certainly, but plenty of turbulence. If you beat up the surface with a gusty blow, it gets wavelets which can lap the filler and blow out the fuel. How about it? It still doesn't change the physical reality that air doesn't *pull* on the wings. You're still singing the last hymn, Alan. We are now discussing how an open tank, with a 100 mph wind blowing over its top, can lose its fuel over the top. Do you think the tank has GREATER pressure due to the venturi effect of the airflow? No. I think that the venturi effect lowers the pressure below the pressure that already exists in the tank. Contrary to what the PP wrote, a tank cannot be sealed if you are to pump fuel out of it. If it were the pump would have to work against a rising pressure difference as it removed fuel from the tank. Hence we know the tanks pressure must be allowed to equalize. If the pressure over an open filler is less than that in the tank -- and assuming the filler is not simply pulling from the air/fuel vapor mixture, then it will pull fuel from the tank if the pressure difference is sufficient to lift the fuel the from its level in the tank to the level of the open filler. But it is being *pushed* out by higher pressure inside, not pulled. -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
#86
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visualisation of the lift distribution over a wing
Alan Baker wrote:
/snip/ Any change in pressure is *by definition* a change in the number of particles in the fluid that are impacting the surface. That assertion is incorrect. You are no dummy so I'm sure you'll correct it when you realize the errors. Sorry, but it's not. Pressure is created by particle collisions. Hmmm...looks like Jim expected too much from you: the kinetic theory of gases has it that pressure may be computed from the temperature AND the density of gases... that is to say, by retaining the SAME molar quantity of gas, and raising its temperature (which translates to a higher velocity), the pressure is increased P.V = R.t and all that.... Put it another way: each "hotter" molecule reverses direction at a surface with greater force. Brian W I'm perfectly aware of that... It took me too long to realise the problem: you have a problem with saying: "Oh yes, I got it worng." People who WON'T do that in technical discussions qualify as people who are just happy to stir up heated debate. I am going to leave this thread now: wrasslin' with pigs gets the hands jest too soiled... Brian W |
#87
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visualisation of the lift distribution over a wing
In article ,
brian whatcott wrote: Alan Baker wrote: /snip/ Any change in pressure is *by definition* a change in the number of particles in the fluid that are impacting the surface. That assertion is incorrect. You are no dummy so I'm sure you'll correct it when you realize the errors. Sorry, but it's not. Pressure is created by particle collisions. Hmmm...looks like Jim expected too much from you: the kinetic theory of gases has it that pressure may be computed from the temperature AND the density of gases... that is to say, by retaining the SAME molar quantity of gas, and raising its temperature (which translates to a higher velocity), the pressure is increased P.V = R.t and all that.... Put it another way: each "hotter" molecule reverses direction at a surface with greater force. Brian W I'm perfectly aware of that... It took me too long to realise the problem: you have a problem with saying: "Oh yes, I got it worng." I didn't get anything wrong. I am and was perfectly aware of the fact that the temperature of a gas indicates a different average speed for the gas molecules and thus a different momentum when the strike a surface. People who WON'T do that in technical discussions qualify as people who are just happy to stir up heated debate. I agree. What of it. I am going to leave this thread now: wrasslin' with pigs gets the hands jest too soiled... You can go. -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
#88
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visualisation of the lift distribution over a wing
Alan Baker wrote:
In article , brian whatcott wrote: Alan Baker wrote: /snip/ Any change in pressure is *by definition* a change in the number of particles in the fluid that are impacting the surface. That assertion is incorrect. You are no dummy so I'm sure you'll correct it when you realize the errors. Sorry, but it's not. Pressure is created by particle collisions. Hmmm...looks like Jim expected too much from you: the kinetic theory of gases has it that pressure may be computed from the temperature AND the density of gases... that is to say, by retaining the SAME molar quantity of gas, and raising its temperature (which translates to a higher velocity), the pressure is increased P.V = R.t and all that.... Put it another way: each "hotter" molecule reverses direction at a surface with greater force. Brian W I'm perfectly aware of that... It took me too long to realise the problem: you have a problem with saying: "Oh yes, I got it worng." I didn't get anything wrong. I am and was perfectly aware of the fact that the temperature of a gas indicates a different average speed for the gas molecules and thus a different momentum when the strike a surface. People who WON'T do that in technical discussions qualify as people who are just happy to stir up heated debate. I agree. What of it. I am going to leave this thread now: wrasslin' with pigs gets the hands jest too soiled... You can go. I feel the same as Brian. This had not been a discussion as much as a troll. OF BLOODY COURSE, the high pressure area under the wing pushes up. So what. It couldn't possibly do that without the reduction of pressure on the top. That's where all the magic is. And you, sir, are a bloody bore. So now, please also dismiss me. |
#89
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visualisation of the lift distribution over a wing
In article ,
cavelamb wrote: Alan Baker wrote: In article , brian whatcott wrote: Alan Baker wrote: /snip/ Any change in pressure is *by definition* a change in the number of particles in the fluid that are impacting the surface. That assertion is incorrect. You are no dummy so I'm sure you'll correct it when you realize the errors. Sorry, but it's not. Pressure is created by particle collisions. Hmmm...looks like Jim expected too much from you: the kinetic theory of gases has it that pressure may be computed from the temperature AND the density of gases... that is to say, by retaining the SAME molar quantity of gas, and raising its temperature (which translates to a higher velocity), the pressure is increased P.V = R.t and all that.... Put it another way: each "hotter" molecule reverses direction at a surface with greater force. Brian W I'm perfectly aware of that... It took me too long to realise the problem: you have a problem with saying: "Oh yes, I got it worng." I didn't get anything wrong. I am and was perfectly aware of the fact that the temperature of a gas indicates a different average speed for the gas molecules and thus a different momentum when the strike a surface. People who WON'T do that in technical discussions qualify as people who are just happy to stir up heated debate. I agree. What of it. I am going to leave this thread now: wrasslin' with pigs gets the hands jest too soiled... You can go. I feel the same as Brian. This had not been a discussion as much as a troll. OF BLOODY COURSE, the high pressure area under the wing pushes up. So what. It couldn't possibly do that without the reduction of pressure on the top. That's where all the magic is. And you, sir, are a bloody bore. So now, please also dismiss me. Look, I started out to clarify the point for those who have the wrong perception of the situation... ....and it turned that there were such people. I explicitly stated that if the OP meant that the low pressure above the wing is responsible for two thirds of the pressure *difference* then he was on solid ground (while allowing as how I didn't know what the precise figures actually were). Ever since then, types like you have been coming in and saying "IT DOESN'T MATTER", when very clearly (because there are people who don't understand the situation) it does. 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. -- Alan Baker Vancouver, British Columbia http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg |
#90
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visualisation of the lift distribution over a wing
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. |
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