FLUID MECHANICS
1.0– Introduction
In everyday life, we recognize three states of matter: solid, liquid or gas. Although
different in many aspects, liquids and gases have a common characteristic in which they
differ from solids: they are fluids, lacking the ability of solids to offer permanent
resistance to a deforming force. Fluids flow under the action of such forces, deforming
continuously for as long as the force is applied. A fluid is unable to retain any
unsupported shape – it flows under its own weight and takes the shape of any solid body
in which it comes into contact.
Fluid mechanics, as the name implies, is the branch of applied mechanics that deals with
the statics and dynamics of liquids and gases. The analysis of the behavior of fluids is
based upon fundamental laws of applied mechanics which relate to the conservation of
mass and energy as well as Newton’s laws of motion. To study compressible fluids, the
laws of thermodynamics should also be included. Fluid mechanics is different from solid
body mechanics for the following reasons:
1. the nature of the fluid itself is different from that of a solid
2. instead of dealing with individual bodies or elements of known mass, we frequently
consider the behavior of a continuous stream of fluid
3. it can be extremely difficult to specify the precise movement of the stream of fluid. It
is often the case that, for the purpose of theoretical analysis, we have to assume ideal,
simplified conditions and patterns of flow.
A few examples in engineering where fluid mechanics is very important include:
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water dams
floating structures
yacht design
flow in pipes
aircraft wings
car aerodynamic design
propellers
hydraulic pumps and turbines
wind turbines
Prof. Ing. Tonio Sant 2017/18
Department of Mechanical Engineering, University of Malta
source: www.orange.nsw.gov.au
Figure 1 – Water dam
source: www.sparetheair.org
Figure 2 – Floating Structure (Oil Rig)
Figure 3 – Yacht
Prof. Ing. Tonio Sant 2017/18
Department of Mechanical Engineering, University of Malta
source: www.rites.com.my
Figure 4 – Pipelines
Figure 5 – Aircraft Wings
Prof. Ing. Tonio Sant 2017/18
Department of Mechanical Engineering, University of Malta
source: www.ahd.tudelft.nl
Figure 6 – Car Aerodynamics
Figure 7 – Propellers
Prof. Ing. Tonio Sant 2017/18
Department of Mechanical Engineering, University of Malta
source: Vattenfall (Horns Rev Offshore Wind Farm, Denmark)
Figure 8 – Wind Turbines
Prof. Ing. Tonio Sant 2017/18
Department of Mechanical Engineering, University of Malta