23-06-2012, 03:33 PM
presentation on SPECIFIC ENERGY CURVE
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FLOW IN OPEN CHANNELS
Flow in open channels is defined as the flow of a liquid with a free surface.
A free surface is a surface having constant pressure such as atmospheric pressure.
SPECIFIC ENERGY
Bernoulli's theorem expresses the energy content of unit volume of fluid as
U = z + h + V2/2g.
The streamlines of the flow are parallel. Along any streamline,
z + h + V2/2g is a constant.
SPECIFIC ENERGY CURVE
Specific energy curve is defined as the curve which shows the variation of specific energy with depth of flow.
SPECIFICATIONS OF THE CURVE
Specific energy curve is actually a combination of two curves, namely, potential energy curve and kinetic energy curve.
E(p)= h is obtained as a straight line.
E(k)=v²/2g is obtained as a parabola.
ALTERNATE DEPTHS
For a given energy value, there generally exists two possible corresponding flow depths. In the diagram above, the alternate depths are labeled y1 and y2and correspond to the subcritical and supercritical flow regions, respectively. This holds true for all energy values except for the critical energy where only one depth is possible, the critical depth.