Fluid Mechanics Flashcards
What is drag ?
- A drag force will slow something down
- Drag is a resistance force
- Drag is caused by a body travelling through a fluid
- Drag acts in opposition to the direction of motion
- Rag has negative effect on velocity
What are the 2 types of drag ?
Surface drag - Friction between surface of an object and the fluid environment
Form drag - Relates to the impact of the fluid environment on an object
What can athletes do to reduce surface drag ?
Swimmers wear specialised smooth suits, caps and shave off their body hair
This makes them smooth
Suits also squash the squishy areas making them more streamline
This reduces the effects of drag and increases velocity
Define form drag ?
Relates to the impact of the fluid environment on an object……Forces affecting the leading edge of an object increases form drag……Forces affecting the trailing edge of an object reduces form drag
What can athletes do to reduce form drag ?
Form drag relates to ‘streamlining’
A large form drag offers ‘less turbulent air’ for anything following
Cyclists will ride very close behind one another (15-30cm) in order to slipstream and save 30% energy
What is streamlining ?
Shaping a body so it can move through fluid effectively and quickly.
Streamlined bodies incorporate a ‘gradual taper’.
The streamlined shape allows air to move past in layers. Enables air to flow smoothly.
Reduces fluid drag
Define turbulent flow
Flow in which the fluid Nader goes irregular fluctuations, or mixing, constantly undergoing changes in magnitude and direction. It increases friction and fluid drag and reduces velocity
Define laminar flow ?
Layers f fluid slide smoothly over one another. They undertake smooth paths, or layers. Less resistant to movement
What factors effect drag ?
Velocity of the moving body
The cross sectional area of the moving body
The shape / surface of the moving body
How does the velocity of the moving body effect drag and how do performers reduce this effect ?
The greater the velocity the greater the drag force
It is important to reduce the effect of drag by streamlining
Helmet: designed to encourage laminar flow.
Bike: lightweight carbon fibre frame, aerodynamic features.
Body position: Head over the bars, low over front wheel, arms tucked.
Clothing: Compressed clothing
How does The cross-sectional area of a moving body effect drag and how do performers reduce this effect ?
A large cross-sectional area will increase drag
Position: reducing cross-sectional area by crouching low.
Position: reducing cross-sectional area by tucking arms in.
How does the shape & surface characteristics of a moving body effect drag and how do performers reduce this effect ?
A more streamlined, aerodynamic shape reduces drag.
Speed skier: Helmet extends to shoulders; more streamlined. Aerodynamic boots are streamlined.
Cycling: Helmet with air ducts aim to reduce drag.
Swimmers: Shave all body hair, create a smooth surface, swimming caps and half body swimsuits.
What is the Bernoulli principle ?
Daniel Bernoulli theorised that an increase In the speed of a fluid occurs as a result in the decrease of pressure
