fluid mechanics - lesson 10 Flashcards
define fluid flow
The natural science of fluids (liquids and gases) in motion.
what are the 3 fluids forces?
Drag (usually works horizontally)
Lift (usually works vertically)
Bouyancy (works vertically)
what is fluid resistance?
As an object moves through a fluid (air or water), it disturbs it.
- The greater the disturbance to the fluid, the greater the transfer of energy from object to a fluid
what are the two factors affecting fluid resistance?
denisty (air)
viscosity (liquid)
how does density affect fluid resistance?
more dense the fluid = the more disturbed the fluid becomes = greater the resistance
how does viscosity affect fluid resistance?
more viscous the fluid (internal resistance of a fluid to flow) = the more disturbed the fluid becomes = greater the resistance
what is the equation of total drag?
total drag = form drag + wave drag +surface drag
what is surface drag?
the drag created due to a fluid moving over an object resulting in friction between the surface of the body and the fluid
what factors affect surface drag?
- Relative velocity of moving object
- Relative roughness of surface object
- Density/Viscosity of the fluid
- Amount of surface area of the object
what is form drag?
Resistance created by the pressure differential between the front and back of an object moving through a fluid
what factors affect form drag?
- cross sectional area of the object presented to the fluid
- velocity of object > higher speed = greater form drag
- surface roughness
- shape of the object
what drag forces affect cyclists?
SURFACE DRAG and FORM DRAG
how can a cyclist reduce surface drag?
- Wear smooth, tight-fitting clothes (minimize surface area)
- Shave legs
how can cyclists reduce form drag?
- Assume streamlined position = reduce cross-sectional area
- Use Aerodynamic rims
- Aerodynamic helmets (teardrop shape)
- Aerodynamic bike components
define wave drag
the drag created by the body at the interface of two fluids interacting whereby waves are created
