A flow is said to be uniform, if the velocity of flow, depth of flow, slope of bed and area of c/s remain constant for a given length of the channel.

whereas, on the other-hand, if velocity depth of flow area of cross section and slope of bed do not remain constant for a given length of pipe, the flow is said to be non uniform.

Specific energy:

The total energy of a flowing liquid per unit weight is given by,

$z + h + \frac{v^2}{2g}$

where, z = height of the bottom of channel above datum.

h = depth of liquid.

v = mean velocity.

If the channel bottom is taken as datum as shown below, then the total energy per unit weight of liquid will be,

$[ E = h + \frac{v^2}{2g}]$ - - - -(1)

SPECIFIC ENERGY

The energy given by equation (1) is known as specific energy hence specific energy of a flowing fluid is defined as energy per unit weight of liquid with repect to the bottom of the channel.

specific energy curve: The curve which shows the variations of specific energy with depth of flow, is known as specific energy curve.

from the equation (1) (i.e. specific energy equation)

$E = h + \frac{v^2}{2g}$

= Ep + Ek

Ep = potential energy of flow = h

Ek = kinetic energy of flow = $\frac{v^2}{2g}$

considering a rectangular channel in which a steady but non uniform i.e. taking place.

Let, Q = discharge

b = width of channel

h = depth of flow

q = discharge per unit width

Then, $q = \frac{Q}{b}$ = constant

velocity of flow, $v = \frac{Q}{Area}$

= \frac{Q}{b \times h}$ $\frac{q}{h} \because \frac{q}{b} = q$ Substituting the values of v in equation (1), we get, $E = h + \frac{q^2}{2gh}$

= Ep + Ek

SPECIFIC ENERGY CURVE