open channel flow

Question 1

define open channel flow

Answer 1

flow of a fluid (usually water) in a conduct with a free surface, where pressure is equal to the local atmospheric pressure

Question 2

where does the force balance in an OCF come from?

Answer 2

between gravity and friction

Question 3

velocity in an OCF is a function of what?

Answer 3

slope, roughness, hydraulic radius

Question 4

what does the hydraulic radius control?

Answer 4

water velocity and discharge

Question 5

define steady flow

Answer 5

water height does not change in time

Question 6

define uniform flow

Answer 6

water height does not vary along the length of the channel

Question 7

what does the froude number represent?

Answer 7

ratio between inertial effects and gravity effects

Question 8

define celerity

Answer 8

velocity at which a small disturbance propagates through a fluid

Question 9

how do waves propagate in still water?

Answer 9

• V = 0
• waves propagate as circles with the very same velocity in each direction
• propagation velocity is equal to celerity

Question 10

how do waves propagate in subcritical flow?

Answer 10

• V < C
• waves propagate downstream with velocity equal to 𝑣+𝐶
• a refraction, with which waves propagate upstream with velocity equal to 𝑣−𝐶

Question 11

how do waves propagate in critical flow?

Answer 11

• V = C
• waves propagate only downstream with respect to the source of perturbation with a velocity equal to 𝑣+𝐶=2𝐶

Question 12

how do waves propagate in supercritical flow?

Answer 12

• V > C
• waves propagate only downstream with velocity equal to 𝑣+𝐶
• circles will detach from the source and will lay only in a conic region of a channel