Question

After heavy rain, water flows on a concrete surface at an average velocity of 1.3 m/s. If the water depth is 2 cm, determine whether the flow is subcritical or supercritical.

Answer 1

The flow is super critical

Step-by-step explanation:

The average velocity of flow is given, V= 1.3 m / s.

Depth of flow, y= 2 cm= 0.02 m

Suppose the flow is in a small rectangular channel.

The number Froude,
`Fr = (V)/(√(gy) )`.

The strength of gravity, g= 9.81 m / s^2,

Replaces the identified values.

`Fr = \frac{1.3 m/s}{\sqrt{(9.81m/s^(2))(0.02 m) }}`

= 2.935

We recognize that the open channel flow is super critical, if the Froude number, Fr > 1.

And the flow is super critical.

Answer 2

Supercritical flow.

Step-by-step explanation:

The Froude number is an useful indicator to determine if flow is subcritical, critical or supercritical, whose formula for an open channel is:

`Fr = (v)/(√(g\cdot y) )`

Then:

`Fr = \frac{1.3\,(m)/(s) }{\sqrt{(9.807\,(m)/(s^(2)) )\cdot (0.02\,m)} }`

`Fr= 2.935`

Which is greater than 1 and, therefore, the flow is supercritical.