Types Of Pressure

Different types of pressures:-

The pressure of the fluid can be measured using two different systems. In one system, the pressure is measured above the absolute zero (complete vacuum) and is called as absolute pressure. In second system, the pressure is measured above the atmospheric and is called as gauge pressure.

Figure17

Absolute Pressure:- It is the pressure measured with reference to absolute vacuum pressure. Gauge Pressure:- In this, by taking the atmospheric pressure as datum, gauge pressure is measured with the help of pressure measuring instruments. Vacuum Pressure:- The pressure which is below the atmospheric pressure is called as vacuum pressure.

The relationship between the above there pressures is as shown below

i. Absolute

g = Gravity in m/s2. v = Velocity in m/s. z = Height in m.

The above equation is known as Euler’s equation of motion.

Bernoulli’s Equation:-

Bernoulli’s Equation is derived from the Euler’s Equation of motion. There are certain assumptions made for deriving the Bernoulli’s Equation and they are as follows. The fluid is ideal i.e zero viscosity. The flow is steady. The flow is incompressible. The flow is irrotational. p/ρg+ v^2/2g+ z=Constant………………………………Eq(6)

Where, p/ρg = Pressure energy unit weight of the fluid. v^2/2g = Kinetic energy per unit weight. z = Potential energy per unit weight.

Bernoulli’s Equation for real fluid

The Bernoulli’s equation was mainly derived for ideal fluids i.e zero viscous fluids hence they are frictionless. But all the fluids are real and has some viscosity and hence offer resistance to flow. When the fluid is flowing there will always be some losses across the sections and Bernoulli’s equation considers all the losses. P_1/ρg+ (V_1^2)/2g+ Z_1= P_2/ρg+ (V_2^2)/2g+ Z_2+ h_l…………………………… Eq(7)

Where h_l = Head loss across the