This document provides an overview of fluid pressure and measurement techniques. It begins with defining key concepts like hydrostatic pressure, Pascal's law, and pressure variation in static fluids. It then describes various devices used to measure pressure, including manometers (U-tube, single column, differential), and mechanical gauges (diaphragm, Bourdon tube, dead-weight, bellows). The document is divided into 5 units covering fluid statics, kinematics, dynamics, pipe flow, and dimensional analysis with the goal of teaching students to calculate pressure, hydrostatic forces, fluid flow, and losses in closed conduits.

1. FLUID PRESSURE AND ITS
MEASUREMENT
(FLUID MECHANICS)
UNIT – I
Dr. Rambabu Palaka, ProfessorJuly-2020

2. Hydrostatic Pressure

3. Syllabus
Unit 1: Fluid Statics
CO1: Calculate Pressure and Hydrostatic forces on different plane surfaces
Unit 2: Fluid Kinematics
CO2: Solve the fluid flow problems using Continuity equation.
Unit 3: Fluid Dynamics
CO3: Calculate the discharges through the Venturi meter, Orifice meter and Pitot tube using Bernoulli’s
equation
Unit 4: Flow through Pipes
CO4: Calculate major and minor losses in closed conduits for different connection pattens.
Unit 5: Dimensional Analysis and Hydraulic Similitude
CO5: Apply the concept of Dimensional Analysis for solving the fluid flow problems and Model Analysis.
Unit 6: Boundary Layer Theory

4. Unit 1: Fluid Statics
1. Introduction (1 Period)
a) Fluid Statics
b) Fluid Kinematics
c) Fluid Dynamics
d) Application of Fluid Mechanics in Civil Engineering
2. Properties of Fluids (3 Periods)
a) Density
b) Specific Weight
c) Specific Volume
d) Specific Gravity
e) Kinematic and Dynamic Viscosity
f) Surface Tension
g) Capillarity

5. Learning Objectives
3. Introduction Fluid Statics (2 Periods)
a). Fluid Pressure
b). Pascal’s Law
c). Hydrostatics Law
c). Pressure variation in a Fluid at Rest
4. Measurement of Pressure (2 Periods)
a). Manometers
b). Mechanical Gauges
5. Hydrostatic Forces on Surface Submerged in Liquid (2 Periods)
a). Vertical Plane Surface
b). Horizontal Plane Surface
c). Inclined Plane Surface

6. Fluid Pressure
Hydrostatic pressure is the pressure that is exerted by a fluid at equilibrium at a
given point within the fluid, due to the force of gravity.
Hydrostatic Law: It states that the intensity of pressure or the rate of increase of
pressure in a vertical direction must be equal to the specific weight of fluid at that
point.
Unit:
N/m2 or Pascal
Density = Mass/Volume
OR
Mass = Density x Volume
= V

8. Pressure variation in a Fluid at Rest

9. Types of Pressure
1. Gauge Pressure
2. Vacuum Pressure  Negative Gauge
Pressure
3. Atmospheric Pressure  101.325 kPa or
1 bar or
14.696 psi
4. Absolute Pressure:
= Gauge Pressure + Atmospheric Pressure
OR
= Atmospheric Pressure – Vacuum Pressure

11. Total Pressure
Total Pressure or Absolute Pressure is sum of
Atmospheric Pressure and Fluid Pressure
Ptotal = Patm + gh
Atmospheric Pressure at the surface of the
Earth stays relatively constant.
The value of the atmospheric pressure at the
surface of the Earth, Patm = 1.01x105 Pa

12. Measuring of Atmospheric Pressure:
Atmospheric air
pressure is often given
in bar or millibars
Unit:
1 bar = 101.325 kPa
= 1.01x105 Pa
= 1013.25
millibar
1 torr = 1mm of
mercury column
Barometer

15. Pascal’s Law
Pascal’s law states that the intensity of pressure at a point in a static fluid is equal
in all the directions (x, y and z directions).
OR
The intensity of pressure at any point in a liquid at rest is
same in all directions. i.e., Px = Py = Pz
This can be derived from
X = 0
(consider Px and Pz cos)
and
Y = 0
(consider weight of fluid in addition to Py and Pz sin)

25. Measurement of Pressure
The pressure of fluid is measured by the following devices:
1. Manometers – by balancing the column of fluid by the same or another column of the fluid
a) Simple Manometers
i. Piezometer
ii. U-tube Manometer
iii. Single Column Manometer
a. Vertical Single Column Manometer
b. Inclined Single Column Manometer
b) Differential Manometers
i. U-tube Differential Manometer
ii. Inverted U-tube Differential Manometer
2. Mechanical Guages – by balancing the column of fluid by the spring or dead weight
a) Diaphragm Pressure Guage b) Bourdon Tube Pressure Guage
c) Dead-weight Pressure Guage d) Bellows Pressure Guage

27. U-tube Manometer

28. U-tube Manometer

29. Single
Column
Manometer

30. Single Column Manometer
Case 1: Small Pressure in
Fluid
Case 2: Very Small Pressure in
Fluid
= L
sin

32. Differential manometers are used to measure the difference of pressures between two
points in a pipe or in two different pipes.
Differential Manometers
Inverted differential manometer

33. Differential Manometers

34. Differential Manometers

39. Reference
Chapter 1-3
(Page 1- 129)
A Textbook of
Fluid Mechanics and Hydraulic Machines
Dr. R. K. Bansal
Laxmi Publications