1. FLUID MECHANICS AND MACHINERY

2. OBJECTIVES To understand the importance of dimensional analysis.
To understand the importance of various types of flow in pumps and turbines.
To understand the properties of fluid.
To learn the fundamentals of compressible flows and incompressible flows.

3. INTRODUCTION
A fluid is a substance that flows under the action of shearing forces. If a fluid is at rest, we know that the forces on it are in balance.
Field of Fluid Mechanics can be divided into 3 branches:
Fluid Statics: mechanics of fluids at rest
Kinematics: deals with velocities and streamlines w/o considering forces or energy
Fluid Dynamics: deals with the relations between velocities and accelerations and forces exerted by or upon fluids in motion

4. Fluids: Statics vs Dynamics

5. FLUIDS
The science and technology of the mechanical properties of liquids is called hydraulics.
Similarly, the science and technology of the mechanical properties of air and other gases is called pneumatics.
The study of hydraulics and pneumatics includes the study of fluids that are not enclosed, such as lakes and air in the atmosphere, as well as pressurized systems that are enclosed.

6. FLUID CONCEPT
Fluid can be defined as a substance which can deform continuously when being subjected to shear stress at any magnitude.
Examples of typical fluid used in engineering applications are water, oil and air.

7. FLUID MOTION streamline Defined instantaneously pathline streakline
has the direction of the velocity vector at each point
no flow across the streamline
steady flow streamlines are fixed in space
unsteady flow streamlines move
pathline
path of a particle
same as streamline for steady flow
streakline
tracer injected continuously into a flow
same as pathline and streamline for steady flow
Defined instantaneously
Defined as particle moves (over time)
Draw Streamlines and Pathlines

8. FLUID FLOWS Laminar flow fluid moves along smooth paths
viscosity damps any tendency to swirl or mix
Turbulent flow
fluid moves in very irregular paths
efficient mixing
velocity at a point fluctuates

9. SURFACE TENSION
Surface tension is a property of liquids where the exposed surface shrinks to the smallest possible area because of unequal forces near the surface.
An example of surface tension is a property of water in a bowl.

10. DENSITY Density of a fluid is defined as its mass per unit volume.
Density has units of kg/m3.
Density of water: 1000 kg/m3
If the density is constant (most liquids), the flow is incompressible.
If the density varies significantly (eg some gas flows), the flow is compressible.

11. HOW TO FIND THE DENSITY Find the mass of the object
Measurement of the amount of matter
(or stuff) in an object
Find the volume of the object
Measurement of the amount of space an object takes up
Density = Mass
Volume

12. WAYS TO INCREASE DENSITY
Keep the same mass AND decrease the volume
Keep the same volume AND increase the mass

13. Water, Oil…and a Superball
The oil is less dense than the water, so it’s on top. The superball is less dense than water, but more dense than oil, so it sinks to the bottom of the oil layer, yet floats on the top of the water layer.

14. MEASUREMENT OF PRESSURE
Barometer (Hg) - Toricelli 1644
Piezometer Tube
U-Tube Manometer - between two points
Aneroid barometer - based on spring deformation
Pressure transducer - most advanced

15. MEASUREMENT OF PRESSURE
A barometer is used to measure the pressure of the atmosphere. The simplest type of barometer consists of a column of fluid.
vacuum
p1 = 0
p2 - p1 = gh
pa = gh
examples h
water: h = pa/g =105/(103*9.8) ~10m
p2 = pa
mercury: h = pa/g =105/(13.4*103*9.8) ~800mm

16. Atmospheric Pressure Pressure = Force per Unit Area
Atmospheric Pressure is the weight of the column of air above a unit area. For example, the atmospheric pressure felt by a man is the weight of the column of air above his body divided by the area the air is resting on
P = (Weight of column)/(Area of base)
Standard Atmospheric Pressure:
1 atmosphere (atm) lbs/in2 (psi) Torr (mm Hg) millibars = kPascals
1kPa = 1Nt/m2