Aerofoil is an interesting and ingenious shape which helps us to fly in the air-plane.
The shape is more curved on the top and less curved at the bottom. It is fixed at an inclined angle to the air plane wings. The working of the foil can be explained in two ways.
1. Bernoulli's principle
Consider wide width pipe connected to a narrow width nozzle. When the water flow from the pipe to the nozzle, the speed of flow increases;consequently we get forceful jet of water from the nozzle. (eg: water fountains). It happens because of the conservation principle. "Same quantity of water must enter and leave the pipe in the same time". Here the water flow is constrained by narrow nozzle; Hence speed has to increase to maintain conservation principle.
In the case of aerofoil; when the plane runs or flies, the air-flow is constrained by top curvature; Hence the wind speed will increase and consequently air pressure drops over the foil (Bernoulli's principle). Below the foil, the wind flows normally and there is high air pressure compared to the top surface. Hence the airplane is lifted up.
2. Molecular theory
If you run in the rain, the rain will fall slantingly on your front body. The back of your body will remain almost dry. Similarly for a foil, most of air molecules will easily flow underneath it. Only less air molecules will flow over the foil because of the curvature and the angle of inclination. Hence more pressure under the aerofoil than above it.
HYDROFOIL:
Hydrofoil is the same structure; attached to the bottom of the boat and moves in water. When the boat goes fast, water pressure lifts up the hydrofoil and the hull of the boat. (You might have seen it in the boat chasing movie scenes)
Once the hull of the boat is lifted up, it is easy to stir and manure the boat. And also less fuel is consumed.
Note: The wind mill blades look like airplane wings. Their design also based on aerofoil. The blades always directly face the flow of wind. Each blade is one by one lifted by the wind flow. Hence they keep rotating.
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The shape is more curved on the top and less curved at the bottom. It is fixed at an inclined angle to the air plane wings. The working of the foil can be explained in two ways.
1. Bernoulli's principle
Consider wide width pipe connected to a narrow width nozzle. When the water flow from the pipe to the nozzle, the speed of flow increases;consequently we get forceful jet of water from the nozzle. (eg: water fountains). It happens because of the conservation principle. "Same quantity of water must enter and leave the pipe in the same time". Here the water flow is constrained by narrow nozzle; Hence speed has to increase to maintain conservation principle.
In the case of aerofoil; when the plane runs or flies, the air-flow is constrained by top curvature; Hence the wind speed will increase and consequently air pressure drops over the foil (Bernoulli's principle). Below the foil, the wind flows normally and there is high air pressure compared to the top surface. Hence the airplane is lifted up.
2. Molecular theory
If you run in the rain, the rain will fall slantingly on your front body. The back of your body will remain almost dry. Similarly for a foil, most of air molecules will easily flow underneath it. Only less air molecules will flow over the foil because of the curvature and the angle of inclination. Hence more pressure under the aerofoil than above it.
HYDROFOIL:
Hydrofoil is the same structure; attached to the bottom of the boat and moves in water. When the boat goes fast, water pressure lifts up the hydrofoil and the hull of the boat. (You might have seen it in the boat chasing movie scenes)
Once the hull of the boat is lifted up, it is easy to stir and manure the boat. And also less fuel is consumed.
Note: The wind mill blades look like airplane wings. Their design also based on aerofoil. The blades always directly face the flow of wind. Each blade is one by one lifted by the wind flow. Hence they keep rotating.
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