Lec 7-8

Question 1

Whats fanning friction factor and when does it apply

Answer 1

fanning friction factor f

Frictional force = f* kinetic E * Area

Characteristic area is the wetted area in contact with the fluid

For flow past stationary bodies or through conduist

Question 2

Hydraulic diameter

Answer 2

Dh = 4Ac/Pw

= 4AcL/Sw

Question 3

What does the friction factor for turbulent flow depend on

Answer 3

Reynolds number and k/Dh

where k is the roughness factor of the conduit wall

Does not depend on geometry or entry length

Question 4

What does the friction factor for laminar flow depend on

Answer 4

Depends on Reynolds number, geometry and entry length

Does not depend on roughness

Question 5

When to use moody diagram

Answer 5

For turbulent flow (must know roughness)

Question 6

What is the friction factor for fully developed laminar flow in a circular tube

Answer 6

f = 16/Re_d

Question 7

What is entry length

Answer 7

The length that it takes for a flow to settle into its velocity profile (become steady velocity profile)

Question 8

How to find friction factor for laminar flow with entry effects

Answer 8

Use graph for laminar flow pressure drop loss at entrance

Question 9

When can we use the M0 diagram

Answer 9

When we have laminar fully developed flow (for any shape)

If it were circular, we would use f = 16/Re_d, but if not we use the resistance

Question 10

How does fanning factor change with external flow

Answer 10

Fk = fKA

But here, K = 1/2 * v_infinity^2 * m
and A is the frontal area of the body

Question 11

What friction factor can you use for reynolds number below 0.5 drag flow for a sphere

Answer 11

f = 24/Re_Dh

Gives you Stoke’s law -> Fk = 3piµDs*v_infinity

Question 12

compliance

Answer 12

C = dV/dPtm