Drag Flashcards
What does skin friction drag + form drag equal?
Profile drag
What does a low Reynolds number indicated about shere/viscous forces?
High forces.
In laminar flow, what level is the Reynolds number?
Low.
What does inertial forces over viscous forces give you?
Reynolds number.
What happens to the laminar flow on a wing if the maximum thickness is moved backwards?
More likely to occur on more of the wing.
What happens to the position of the transition point as the angle of attack increases?
It moves forward.
How is the coefficient of lift and velocity proportional?
CL & 1/v^2
How is the stall speed proportional to weight?
Vstall & -/weight
How do you measure the load factor?
Lift/weight.
Why does form drag occur?
Due to pressure gradient.
By reducing the frontal area of an aircraft, you can reduce what type of drag?
Form drag.
What is free stream flow?
Air not affected by an aircraft.
What would you say about turbulent airs velocity gradient?
Steep velocity gradient.
Compared to laminar flow, does turbulent flow have more or less energy?
More energy.
What type of airflow is less likely to cause stalling?
Turbulent flow.
Why does the air have to be turbulent post the point of max thickness?
Pressure gradient opposes the airflow.
What happens if the air travelling over the wing losses more energy than the energy needed to oppose the adverse pressure gradient shere forces?
Seperation.
What type of airflow is resistant against separation?
Turbulent airflow.
Given a constant load factor, which of these statements about the variation of induced drag with changes of speed and mass are correct or incorrect?
- When speed decreases, induced drag decreases.
- When mass decreases, induced drag increases.
Both incorrect.
True or false : Assuming no flow separation, the strength of wing tip vortices increases as the angle of attack increases.
True
What kind of drag will you find on a wing with no lift?
Parasite
What is the point on the wing about which the pitching moment created by the lift does not change with changes in AoA.
Aerodynamic centre
True or false : the aerodynamic centre cannot move.
True
At subsonic flight, what percentage of MAC is the aerodynamic centre located at?
25%
