WITW?bob012345 said:
bob012345 said:
Yeah, like the others said, this implies to me plane moving in still air vs plane still and air moving (in a wind tunnel). Short answer is there is no difference.bob012345 said:
Are you saying the minimum power you need in a perfectly designed tunnel matched to this wing, with no waste, would have the same power as the plane needed to provide thrust to move the plane forward in the first case?russ_watters said:
You're saying the answer to my original question is that it takes far more power to move enough air over the wings to generate enough lift than moving the plane thought the air to generate the same lift. Thanks.FactChecker said:
To be more exact, I would say that it takes more to generate the same lift using the same aerodynamics. I can't say that there is no way to concentrate an airstream of smaller diameter to make the same total lift with different aerodynamics going on. I wouldn't know about that.bob012345 said:
You actually asked two questions; one was about airflow and the other about power. Let me separate them: the airflow (more specifically the airflow velocity) is the same. the power is higher in the wind tunnel than on the plane because in addition to moving the air past the plane, the wind tunnel fan has to move the air through the wind tunnel. And to be useful, the wind tunnel has to be big enough that the test model doesn't have a big impact on the flow though the tunnel.bob012345 said:
That is a good way of looking at it. It means that to mimic the flight aerodynamics the wind tunnel must be so big that it contains all the model disturbance. Ideally, the walls of the wind tunnel should not come into play at all and should parallel the airflow streamlines.russ_watters said:
I agree. It doesn't take nearly as much power to fly a piloted airplane as it does to generate a huge-area airflow in a theoretical large wind tunnel. The two situations are not comparible. A wind tunnel model can be scaled down to as little as 1/100th size.
Somewhat non-intuitively problems arrive matching dimensionless quantities of fluid mechanics between scaled model and object.FactChecker said:
I agree. It may be possible to more efficiently flow air at higher speeds over smaller local areas to generate lift. They do this with 'blown wings' to some extent already.FactChecker said:
The amount of air flow passing over a wing directly affects the amount of lift it can generate. As air flows over the curved surface of a wing, it creates an area of low pressure above the wing and an area of high pressure below the wing. This pressure difference creates a force that lifts the wing upwards.
Several factors can impact the amount of air flow required for wing lift, including the shape and size of the wing, the air density, the angle of attack, and the speed of the aircraft. A larger wing or a higher angle of attack will require more air flow to generate lift, while a smaller wing or a lower angle of attack will require less air flow.
The minimum air flow required for wing lift is known as the stall speed. This is the slowest speed at which an aircraft can fly while still maintaining enough air flow over the wings to generate lift. The stall speed varies depending on the factors mentioned above, but it is an important consideration for aircraft design and operation.
Air density is a major factor in determining the amount of air flow required for wing lift. Higher air density means there is more air molecules passing over the wing, which can generate greater lift. This is why aircraft typically require more air flow at higher altitudes where the air density is lower.
The required air flow for wing lift can be calculated using various equations and aerodynamic principles, such as Bernoulli's principle and the lift equation. These calculations take into account the factors mentioned above, as well as the wing's shape and the aircraft's weight and speed. These calculations are crucial for designing efficient and safe aircraft.
