TO PRESENT ABOUT
TOPIC 5 & 7
THE CONCEPT OF FLOW IN MOTION DUE
TO PRESENCE OF SHEAR STRESS
A stress is defined as a force per unit area, acting on an
infinitestimal surface element.
Stresses have both magnitude (force per unit area)
and direction, and the direction is relative to the surface on
which stress acts.
There are normal stresses and tangential stresses.
Pressure is an example of a normal stress, and act inward,
toward the surface,and perpendicular to the surface
THE BEHAVIOR OF FLUID IN PIPES
Laminar flow generally happens when dealing with small pipes and low flow velocities.
In laminar flow the motion of the particles of fluid is very oderly with all particles moving
in straight line parallel to the pipe walls.
In turbulent flow vorticles and wakes make th eflow unpredictable. Turbulent flow
happens in general at high flow rates and with larger pipes.
Transitional flow is a mixture of laminar and turbulent flow, with turbulence in the center
of the pipe, and laminar flow near the edges. Each of these flows behave in different
manners in terms of their frictional energy loss while flowing,and have different equations that predict their behavior.
THE ENERGY LOSSES AND MINOR LOSSES IN PIPE SYSTEM
The total energy lose in a pipe system is the sum of the major and
Minor losses occur due to a change in the magnitude of velocity. For
a long pipeline, minor losses are small as compared to loss due to
friction, which may be neglected without serious error.
The minor losses of energy may be occur at the following places :
Entrance of pipe in a pipe
Exit of pipe
Sudden enlargement in a pipe
Sudden contraction in a pipe
Bend and pipe fittings
ENERGY LOSSES THAT OCCUR IN REAL PIPELINE
In real fluid flows, losses occur due to the resistance of the pipe walls
and the fittings to this flow and lead to an irreversible transformation
of the energy of the flowing fluid into heat.
Two forms of losses can be distinguished :
losses due to friction and