Bernoulli Equation
The Bernoulli Equation:-
Bernoulli's equation says in an ideal situation, the TOTAL HEAD = constant.
There are assumptions; An ideal fluid (no friction) flowing steadily:-
- The fluid is incompressible and nonviscous.
- There is no energy loss due to friction between the fluid and the wall of the pipe.
- There is no heat energy transferred across the boundaries of the pipe to the fluid as either a heat gain or loss.
- There are no pumps in the section of pipe under consideration.
- The fluid flow is laminar and steady state.
PRESSURE DENSITY :-
Pressure in a fluid is like the energy per unit volume (energy density). From the definition of pressure:
Here is the Bernoulli equation in terms of energy per unit volume;
Note that this correponds exactly with the conservation of energy equation. Where pressure = spring energy, velocity = kinetic energy and height = potential energy.
SE1 + KE1 + PE1= SE2 + KE2 + PE2
Where: PE1 = mgh1 and KE1 = 0.5mv12 and SE1 = 0.5kx12
Where: PE1 = mgh1 and KE1 = 0.5mv12 and SE1 = 0.5kx12
TOTAL HEAD:-
Total Head (also called Total Dynamic Head) is the sum of the three components; pressure head, velocity head and potential head. From the above equation, divide by g. Head is a simple way to think of each term (pressure, velocity and height) in terms of the number of METRES of that fluid it is equivalent to.
- All terms are head (m), which is measured in the working fluid.
- You can use gauge or absolute pressure throughout, but gauge is normal
- Continuity equation is also true (and often needed to solve the question)
- Ideal fluid is assumed (no friction)
Bernouli's Equation requires velocity. This is usually found using the continuity equation.
= V / t = A
Since most pipes are round, this gives;
v1d2/4 = v2d2/4
or
Bernoulli Equation
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