Fluid mechanics Flashcards
Define fluid mechanics
Fluid mechanics is the study of forces acting on a body travelling through the air or water
2 forces in fluid mechanics and their roles
Air resistance: the force acting to oppose the motion of a body through air.
Drag: the force acting to oppose the motion of a body through a fluid
These are both types of fluid friction. These need to be reduced in order to maximize performance
5 main factors that impact the magnitude of these forces
- Velocity
- Mass
- Frontal cross-sectional area
- Streamlining and shape
- Surface characteristics
Effect of velocity on AR or D
The greater the velocity the greater the air resistance or drag.
Usually in sport we want to increase velocity not decrease it, as it is beneficial to performance, therefore we need to manipulate other factors in order to decrease AR or D.
E.g. Cycling around a track, hitting a tennis ball harder
Effect of mass on AR or D
The mass of a body affects what happens to its motion as a result of air resistance and drag.
The greater the mass, the less its motion is changed by these forces. Bodies with a small mass slow down quickly due to fluid friction.
Air resistance then decreases due to reduced velocity.
E.g. A badminton shuttle
Effect of frontal cross sectional area on AR or D
This is the area of the part of the body that presents first to the fluid it is moving through.
The smaller this frontal cross-sectional area is, the less fluid friction (air resistance or drag) acts.
E.g. a golf ball has a smaller frontal cross-sectional area than a football so will be less affected.
Effect of streamlining and shape on AR or D
Fluid friction is minimised by using the optimal shape or position.
The more streamlined or aerodynamic the body or object in motion, the smoother the air or water flow around it, so the lower the AR or D.
E.g. A swimmer adopts a streamlined shape to minimise drag.
E.g. A cyclist adopts a crouched position and has a teardrop shaped helmet.
Effect of surface characteristics on AR or D
This relates to the smoothness of the surface of a body.
The smoother the surface the lower the air resistance or drag.
E.g. A swimmer shaves their body hair to make their skin smooth.
E.g. A cyclist wears a smooth tight fitting suit.
