Chapter 2

Question 1

The common charactaristics of turbulent flows:

Answer 1

1. turbulent flows are rotational and 3D
   
   1. vorticity fluctuations are important
2. flows are dispersive (energy is lost as they get smaller and smaller)
   
   1. to maintain the turbulent energy must be supplied
3. fluid motions are very unpredictable (statistical/ emperical used)
4. the rate of transfer and mixing >> (several order larger than) the rate of molecular diffusion.
   
   1. rate of molecular diffusion can be neglected

Question 2

difference between non turbulent flows and turbulent flows

Answer 2

Non turbulent flows:

• Non tangental force at bounday
• laminar

Turbulent flows

• express tangental forces

Question 3

tangental forces are known as

Answer 3

shearing stresses which are related to the fluid viscocity

fluid viscocity: tendancy to resist the flow

Question 4

shearing stress=

Answer 4

u is the dynamic viscocity coefficient

Question 5

kinematic viscocity coefficient:

Answer 5

V = u/p

u = Dynamic viscocity coefficeint

p=density

Question 6

such flows are

Answer 6

impossible to predict

Question 7

we quantify the mean state by

Answer 7

performing averaging operation on the atmospheric properties

Question 8

any instat value/ actual value (a) is decomposed into

Answer 8

a mean (a-) and a fluctuating part (a’)

a-= 1/N Σ^N_i=1 a_i

Question 9

the reynolds averaging follows three rules:

Answer 9