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Flow properties, such as depth of flow area of cross section and velocity of flow vary with respect to distance is called Non-uniform flow.

**Varied Flow**

Flow properties, such as depth of
flow area of cross section and velocity of flow vary with respect to distance
is called Non-uniform flow.

It is,
otherwise, called as varied flow. The varied flow is broadly classified into
two

types:

1) Rapidly
varied flow (R.V.F)

2) Gradually
varied flow (G.V.F)

If the depth of flow changes quickly over a small
length of the channel, the flow is said to be gradually varied flow (GVF).
Example: Back water in a dam.

The
following assumptions are made for analyzing the gradually varied flow:

1. The flow
is steady

2. The
pressure distribution over the channel section is hydrostatic, i.e.,
streamlines are practically straight and parallel.

3. The head
loss is same as for uniform flow.

4. The
channel slope is small, so that the depth measured vertically is the same as
depth measured normal to the channel bottom.

5. A channel
is prismatic.

6. Kinetic
energy correction factor is very close to unity.

7. Roughness
coefficient is constant along the channel length

8. The
formulae, such as Chezy's formula, Manning's formula which are applicable, to
the uniform
flow are also applicable for the gradually varied flow for determining slope of
energy line.

Tags : civil - Applied Hydraulic Engineering: Gradually Varied Flow

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