Fluid mechanics Flashcards
Define fluid mechanics
The study of an object or body that travels through a liquid or gas
What are the 2 dynamic fluid forces?
Lift
Drag
Define drag force
A force that acts in opposition to motion
What are the 2 types of drag?
Surface drag
Form drag
What is surface drag?
Friction between the surface of the object and the fluid environment
What is form drag?
The forces affecting the leading edge of an object
How can form drag be reduced?
Decrease frontal surface area of an object
Streamlining a body/object
How can surface drag be reduced?
Create a smoother surface
Create a smaller surface area
What factors affect the drag of a body/object?
Velocity of the moving body
Cross sectional area of the body
Shape and surface characteristics of moving body
Define streamlining
Shaping a body so it can travel through a fluid fast and effectively
Define lift force
A force that causes body to move perpendicular to the direction of travel
Define angle of attack
The tilt of a projectile relative to the air flow
Define Bernoulli principle
Where air molecules exert less pressure the faster they travel and more pressure when they travel slower
Explain Bernoulli principle in relation to a discus
Angle of attack changes the air flow
Air flowing over the top has a greater distance to travel, causing higher velocity and therefore low air pressure
Air flowing underneath has less distance so lower velocity therefore a greater air pressure
This high air pressure exerts the lift force, allowing discus to remain in flight for longer
What is the optimal angle of attack for a discus?
25-40 degrees
Explain the Bernoulli principle in terms of an F1 car
Angle of attack of spoiler is downwards to exert a down force
Air travels slower over the top of the car and faster underneath the car
Lower air pressure on top of the car causes a down force, creating a stronger grip between the tires and the road
Car is able to turn corners at greater speeds
What kind of flow does a streamlined body encourage?
Laminar
What kind of flow does a less streamlined body encourage?
Turbulent
What are the characteristics of turbulent flow?
Irregular fluctuations
Changes in magnitude and direction
Increased friction
What are the characteristics of laminar flow?
Fluid moves smoothly
Undertake smooth paths/layers
Less resistant to movement
