Flow Rate

Question 1

How do we distinguish laminate flow from turbulent

Answer 1

Reynolds Number (Re) if laminar (Re < 2000) and turbulent flows (Re > 4000) in between is called transitional flow.

Question 1

Define similitude

Answer 1

The relation between a prototype and its model. The types of similarities that must exist for complete similitude:
- Geometric similarity (scale ratio)
- Kinematic similarity (accel & velo)
- Dynamic similarity (forces on body)

Question 2

How do you work out Reynolds Number (Re)

Answer 2

Re = (ρuL)/μ
= inertial force/viscous forces

μ = dynamic viscosity
L = characteristic length
(height, width or diameter)
ρ = fluid density
u = velocity

Question 3

define inertial force and viscous forces

Answer 3

inertial force = forces that cause fluid to move

viscous forces = frictional forces due to viscosity

Question 4

How do you calculate the maximum velocity in a pipe and between two parallel plates

Answer 4

Pipe: Vmax = 2 x Vmean
Parallel plate: Vmax = 3/2 x Vmean

Question 5

Equation to calculate the velocity at a certain height in a pipe

Answer 5

V/Vmax = 1 - (r/R)^2

R = radius
r = distance from centre point

Question 6

How to calculate the loss of head due to friction

Answer 6

Darcy equation

h = Δp/ ρg
h = 4f * (L*Vmean^2) / (2gD)

Question 7

Equation for hydraulic diameter, D

Answer 7

D = 4a/p

a = cross sectional area of flow
p = perimeter of cross section

Question 8

Calculate friction in a laminar flow

Answer 8

f = 16/Re

Question 9

Calculate the power required to maintain the flow

Answer 9

P = ρgQh

Question 10

Calculate friction in a turbulent flow

Answer 10

f = 0.079/Re^1/4

Question 11

How do you work out the necessary diameter increase to maintain flow if wall roughness if changed

Answer 11

Calculate relative roughness and use the moody chart to calculate new Re