1.1-3

Question 1

what is a laminar flow

Answer 1

A fluid that stays together
Re<2000

Question 2

What is a turbulent flow

Answer 2

A fluid that breaks up
re>4000

Question 3

symbol for dynamic viscosity

Answer 3

µ

Question 4

Velocity profiles for three types

Answer 4

Laminar - parabola
turbulent - flatter with smaller boundary layer
ideal - flat

Question 5

the three main flows

Answer 5

• free stream, largely undisturbed
• boundary layer, adjacent to the body
• separated regions, the wake where the boundary layer seperates

Question 6

cause of drag (rels)

Answer 6

-recirculation in wake
-energy loss in wake
-∴ less pressure behind
-higher pressure in front of stagnation point
-∴ increased pressure in front

Question 7

what is it called when the wake oscillates

Answer 7

vortex shedding

Question 8

3 dimensions used

Answer 8

M, L, T

Question 9

what is viscosity

Answer 9

ability to resist a sheer stress

Question 10

relationship between stress an strain for a solid and a liquid

Answer 10

-solid: strain is proportional to stress
-liquid rate of change of strain proportional to stress

Question 11

what is strain in a fluid

Answer 11

change in angular distance
for a small strain, ø =x/y

Question 12

Newtons law of viscosity

Answer 12

T=µdu/dy

Question 13

how dynamic viscosity changes with temperature

Answer 13

increase for gas
decrease for liquid

Question 14

density water

Answer 14

1000kg/m3

Question 15

is shear stress more or less near the boundary

Answer 15

more as T is proportional to du/dy