Fluid dynamics

Question 1

Explain how composition and flow characteristics of a fluid affect fluid forces

Question 2

Define ‘drag’

Question 3

What are the componenets of ‘Drag’

Answer 3

• Density (ρ): mass:volume ratio i.e. specific weight
• viscosity (cps): internal resistance of a fluid to flow

Question 4

What factors affect the magnitude of each drag componenet?

Question 5

Define ‘lift’

Question 6

How is ‘lift’ generated?

Question 7

Relative velocity

Answer 7

is the vector subtraction of the bodys velocity from that of the fluid
-Head wind example:
Vhw = Vp - Vhw
Vhw = -15m/s - 5m/s = 20m/s (persons velocity is -ve becuase going against wind vector)

• Tail wind example:
  Vtw = Vp-Vtw
  Vtw = 15m/s - 5 = 10m/s

Question 8

Forced acting on a body related to fluid

Answer 8

Buoyancy
Archimedes principle

Fb = ρ x g x v
OR
Fb = V x d x γ

Question 9

What is Buoyancy?

Answer 9

The upwards acting fluid force is EQUAL to the weight of the fluid displaced by the body.
*thrust force
Weight of object (in air) - thrust force (buoyancy) = apparent weight
- Buoyancy forces act through our centre of VOLUME

Question 10

What is the Archimedes principle? (law)

Answer 10

the buoyant force acting on a body is equal to the weight of the fluid displaced by the body
Weight of object (in air) - thrust force (buoyancy) = apparent weight

Question 11

Body fat % calculation

Answer 11

(495/body density) - 4.142) * 100 = body fat percentage

Question 12

Body density calculation

Answer 12

Wdp / ((Wdp - Wup) / Wρ - RV) = body density