how much air does an A380 shift?
Discussion
Simpo Two said:
I think you're thinking of boats or airships... winged flight is not about simple displacement but lift.
If its a similar process to say a propeller in water then surely it still has to displace its own mass regardless of lift?.I will ask my bro, he is a fluids engineer
I need hard info!!blueg33 said:
If its a similar process to say a propeller in water then surely it still has to displace its own mass regardless of lift?.
In what timeframe? Does it have to displace its own mass every second, or every minute? If it displaced its own mass all the time it would just float...In your original question I thought you wanted to know the weight of air that the voulme of an A380 occupied. Then I thought you wanted to know the volume of an A380-sized void as it carved a track to its destination. Now I have no idea...
Simpo Two said:
In what timeframe? Does it have to displace its own mass every second, or every minute? If it displaced its own mass all the time it would just float...
In your original question I thought you wanted to know the weight of air that the voulme of an A380 occupied. Then I thought you wanted to know the volume of an A380-sized void as it carved a track to its destination. Now I have no idea...
Sureley it can only displace its own mass once In your original question I thought you wanted to know the weight of air that the voulme of an A380 occupied. Then I thought you wanted to know the volume of an A380-sized void as it carved a track to its destination. Now I have no idea...
Perhaps the op means how much air does it push out of the way? If so then frontal area is probably more of a factor, along with altitude, air pressure and temp.blueg33 said:
Sureley it can only displace its own mass once
No, that's volume.Blackpuddin said:
The second one, how much air does an A380 shift as it's flying along, in whatever timeframe you fancy.
OK, work out the frontal area of an A380 and multiply it by the distance from A to B. That will give you an aeroplane-shaped 'slot' in cubic metres or whatever units you like.I think the problem is the word 'shift', which is a bit vague.
Edited by Simpo Two on Friday 13th April 17:22
Simpo Two said:
blueg33 said:
Sureley it can only displace its own mass once
No, that's volume.blueg33 said:
You are right (I must be having a senior moment. I am correct though in thinking that the displacement of a boat is equal to its mass?
Yes, it's the 'Eureka' moment - 'This exclamation is most famously attributed to the ancient Greek scholar Archimedes. He reportedly proclaimed "Eureka!" when he stepped into a bath and noticed that the water level rose—he suddenly understood that the volume of water displaced must be equal to the volume of the part of his body he had submerged. This relation is known as Archimedes' principle. He then realized that the volume of irregular objects could be measured with precision, a previously intractable problem. He is said to have been so eager to share his discovery that he leapt out of his bathtub and ran through the streets of Syracuse naked.'So a 10 ton boat will go down until 10 tons of water is displaced - and then the boat is floating. Same is true for airships and balloons - but not aeroplanes, hence the phrase 'heavier than air flight'
Nimby said:
Won't it depend on altitute?
It displaces its own volume of air (obviously), but that volume will weigh a lot less at 30,000 feet than sea level.
Sort of; it would displace less "standard air" (Sea level, 20 degrees C) but the same amount of actual air.It displaces its own volume of air (obviously), but that volume will weigh a lot less at 30,000 feet than sea level.
A quick google suggests that at takeoff the engines shift two million cubic feet per minute each, or eight million in total.
Cross-section area * velocity (in metres/second) * density of air at that altitude.
Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
Simpo Two said:
blueg33 said:
You are right (I must be having a senior moment. I am correct though in thinking that the displacement of a boat is equal to its mass?
Yes, it's the 'Eureka' moment - 'This exclamation is most famously attributed to the ancient Greek scholar Archimedes. He reportedly proclaimed "Eureka!" when he stepped into a bath and noticed that the water level rose—he suddenly understood that the volume of water displaced must be equal to the volume of the part of his body he had submerged. This relation is known as Archimedes' principle. He then realized that the volume of irregular objects could be measured with precision, a previously intractable problem. He is said to have been so eager to share his discovery that he leapt out of his bathtub and ran through the streets of Syracuse naked.'So a 10 ton boat will go down until 10 tons of water is displaced - and then the boat is floating. Same is true for airships and balloons - but not aeroplanes, hence the phrase 'heavier than air flight'
Zad said:
Cross-section area * velocity (in metres/second) * density of air at that altitude.
Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
Beat me too it but i agree with the maths shown above.Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
BarnatosGhost said:
If I remember correctly I think he'd been challenged to work out whether the king's crown had been made of pure gold, or of a gold alloy. Displacement gave him the ability to work it out, since a pure gold crown would displace the same amount as a lump of gold of the same weight as the crown. An alloy crown would be displace a different amount to that same lump of gold.
That's like asking 'Which is heavier, a pound of lead or a pound of feathers?'Assuming both crowns were heavier than water, if they were the same volume they'd displace the same amount of water. 1cm3 of metal displaces 1cm3 of water; it has no option whatever it is (unless it floats). But combining volume with weight gives density, which is probably what you were thinking of
Simpo Two said:
BarnatosGhost said:
If I remember correctly I think he'd been challenged to work out whether the king's crown had been made of pure gold, or of a gold alloy. Displacement gave him the ability to work it out, since a pure gold crown would displace the same amount as a lump of gold of the same weight as the crown. An alloy crown would be displace a different amount to that same lump of gold.
That's like asking 'Which is heavier, a pound of lead or a pound of feathers?'Assuming both crowns were heavier than water, if they were the same volume they'd displace the same amount of water. 1cm3 of metal displaces 1cm3 of water; it has no option whatever it is (unless it floats). But combining volume with weight gives density, which is probably what you were thinking of
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