Page 79 - ebook fluid mechanics_finalize

FLUID MECHANICS

4.5 Definition of Bernoulli’s Equation

Bernoulli’s Theorem states that the total energy of each particle of a body of fluid is the
same provided that no energy enters or leaves the system at any point. The division of this

energy between potential, pressure and kinetic energy may vary, but the total remains

constant. In symbols:

p v 2
H = z + + = constan t

 2 g

Do you know :

The Bernoulli equation is named in honour of Daniel Bernoulli (1700-1782). Many

phenomena regarding the flow of liquids and gases can be analysed by simply using the
Bernoulli equation.

By Bernoulli’s Theorem,

Total energy per unit weight at section 1 = Total energy per unit weight at section 2

p v 2 p v
z + 1 + 1 = z + 2 + 2
1
 2 g 2  2 g

z = potential head

p
= pressure head


v
2 = velocity head
2 g

H = Total head

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