Aerodynamics Flashcards
What is aerodynamics?
The study of the properties of moving air and the interaction between the air and the solid bodies moving through it
What is the continuity equation?
As speed increases, the cross sectional area decreases so long as density remains constant
What is the relationship between the velocity and the cross-sectional area in the continuity equation?
They are inversely proportional to one another
Give the continuity equation formula
A1V1 = A2V2
What is the property of air in the subsonic region?
Incompressible
Why is air incompressible in the subsonic region?
The flying body does not attain speeds necessary to compress the air
If there is no disturbance, air streamlines are what to one another?
Parallel to each other
When the diameter increases and speed decreases, what type of outlet is this classed as?
A diffuser outlet
What is a jet outlet?
An outlet where the diameter decreases and the speed increases
What does Bernoulli’s Principle state?
Total Pressure = Static Pressure + Dynamic Pressure
Total Pressure is always constant
If the valve is closed, describe static, dynamic and total pressure
Static pressure is at its maximum
Dynamic pressure is 0
Total pressure is at its maximum
As a valve starts to open, describe what happens in relation to pressure
Static pressure decreases as dynamic pressure increases
Total pressure remains at its maximum
What is the Point of Stagnation?
The point on the leading edge where dynamic pressure is 0 or the total pressure is equal to the static pressure
How do you calculate the total pressure?
Total pressure = Static Pressure + Dynamic Pressure
How is lift produced?
Higher pressure below the wing
Lower pressure above the wing
The difference in static pressure acts on the surfaces of the wing to create a lifting force
What is up-wash?
The upward flow of air directly ahead of the Leading Edge
What is down-wash?
The downward flow of air directly ahead of the Trailing Edge
What is the Magnus Effect?
Mechanically induced circulation
Describe the pressure waves using the Magnus effect when the cylinder is stationary
Static pressure on the upper surface of the cylinder is equal to the static pressure on the lower surface
No differential pressure means no lift
Describe the pressure waves using the Magnus Effect on a rotating cylinder
The circulatory flow causes an increase in local speed on the upper surface and a decrease in local speed on the lower surface
Difference in pressure generates lift
If the cylinder rotates at a higher speed, what happens to the pressure?
Decrease
What relation does speed have to pressure?
They are inversely proportional
What is the general rule for vortices?
They come in a pair, clockwise and anti-clockwise
What is a wing profile?
A cross-section of a wing