9. Free Surfaces

Question 1

How do you approximate surface wave speed?

Answer 1

c = √(g y) where y is depth of water + wave

Question 2

What is Froude number (Fr)

Answer 2

Fr=V/c

where c is surface wave speed and V is mean flow velocity

Question 3

What is a hydraulic jump and how does it occur?

Answer 3

When flow goes from super critical (Fr>1) to sub critical (Fr<1), as the stream moves downstream, a hydraulic jump occurs when the depth of water changes.

Question 4

What are the characteristics of sub-critical flow

Answer 4

Tranquil, disturbances bi-directional, ripple on pond

Speed of disturbance faster than mean stream flow (concentric rings)

Question 5

What are the characteristics of critical flow

Answer 5

Concentric rings with centre on outer periphery

Question 6

What are the characteristics of super-critical flow

Answer 6

rapid, shooting disturbances

Rings outside each other, first ring swept downstream. Disturbances cant move upstream