CIVL151 FLUID MECHANICS
MOCK Exam
Student Name.
Student ID.
Notes
(1) All computation steps, i.e. all working, must be shown clearly without them, no
score will be given
(2) Assumptions made must be clearly stated and justified
(3) Proper units must be at
CIVL151 FLUID MECHANICS
MOCK Exam
Student Name.
Student ID.
Notes
(1) All computation steps, i.e. all working, must be shown clearly without them, no
score will be given
(2) Assumptions made must be clearly stated and justified
(3) Proper units must be at
Viscous and Turbulent flows
1
Viscous and turbulent flows
The force F required to move the top layer of area A at a
velocity V is found experimentally to be:
AV
F
y
2
By introducing a proportional constant , the absolute viscosity
of the fluid,
AV
F=
y
In
Form Resistance
1
Flow pattern around a circular cylinder
Flow of an ideal fluid
For steady irrotational flow of an ideal fluid, the assumed absence of viscous
effect results in the complete lack of resistance to motion regardless of how
much the fluid is
Pipe Flow
1
General equations
All steady flow pipe flow problems may be solved by application of the
continuity and Bernoulli equations. An effective method of solving pipe flow
problems is by graphical representation of the head losses caused by surface
Surface Resistance
1
Flow pattern near a solid boundary
Considering the flow of a viscous fluid near a solid boundary,
e.g. flow past a streamline body
2
Flow pattern near a solid boundary
The flow pattern depends on:
Viscous action provided by the viscou
Flow measurements
1
Discharge through orifices, sluices and weirs
Consider the discharge form a two-dimensional orifice, such as
an air jet into the atmosphere.
Coefficient of contraction
Ac b
Cc =
= for 2 D cases
A0 d
Apply Bernoulli equation from 1 to 2
Chap 7 External Flows
Chap 6 focused on closed conduit ow (internal ow), i.e., pipe ow,
and concerned its energy dissipation.
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This chapter focus to ow around a body and concerns its force.
Boundary layer
Dimensional analysis
Similitude
Model scaling
1
Dimensional analysis
Require no analytical knowledge
Choose relevant variables
Use a theorem to obtain dimensionless groups, mostly
ratios of forces
Inertial force
Viscous force
Gravitational force
Es
One dimensional concept of conduit flow
1
For problems concerning conduits, it is usually convenient to
consider a conduit as being in effect a single stream tube, where
quantities such as velocities and heads at various section are
expressed as the avera
Flow patterns
1
Types of flow
Laminar - fluid layers flow alongside one another either at the
same or at slightly different velocities and there is no mixing of
fluid particles.
Turbulent accounts for about 99% of real flow situations. There
are velocity
Equations of motion
1
For unsteady, non-uniform flow, the absolute velocity in the x
direction is
v x = fn( x, y, z, t )
The acceleration in the x direction is
dv
ax = x
dt
v
v x v x y v x z
= x+ x
+
+
t
x t y t z t
v
v
v
v
= x + vx x + v y x + vz x
t
x
Chap 8 Ideal-Fluid Flows
Previous chapter developed mainly for one-dimensional ow, that is,
ow in which the average velocity at each cross section is used and
variations across the section are neglected.
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Chap 3 Fluid Flow Concepts and Basic Control Volume Equation
Introduce concepts needed for analysis of uid motion. Derive basic equations that enable us to predict uid behavior. Including Continuity equation Equation of momentum First and second laws of
Chap 2 Fluid Statics
Considering Newtons second law, d(mv) =F dt The goal of this chapter: d(mv) =0 dt Fluid statics Solid body acceleration (special case) Can be converted to statics by using a moving frame of reference No relative motion of adjacent uid
Stability of floating vessels
1
Stability of floating and submerged bodies
A floating or submerged body is said to have a stable stability
when a small angular displacement in any direction will set up a
restoring moment that tends to return it to its ori
Fluid properties
1
Definition of a fluid
A fluid is a substance that deforms continuously when
subjected to a shear stress, no matter how small that shear
stress may be. A shear force is the force component tangent
to a surface, and this force divided by
Fluid statics, hydrostatics
1
Fluid statics implies fluid at rest
No shear force is considered because it does not occur in a static
fluid. Therefore the only stress is normal stress or pressure.
In a static fluid, the pressure at a point is the same in a
Chap 5 Dimensional Analysis and Dynamics Similitude
Why dimensional analysis?
Example 1: Reynolds experiment: laminar ow and turbulent ow.
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Question: when the ow is turbulent?
Turbulent ow: intuitively fo
Chap 4 Basic Governing Differential Equations
Control volume approach can be used to calculate resultant force and
momentum of force and line of action.
Reynolds transport theorem (connection between control volume and
system)
dN
=
dV +
v dA
dt
t cv
cs
Th
Course material can be found on web http:/lmes2.ust.hk
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Chap 1 Fluid Properties
Fluid Density Viscosity Surface tension effect Vapor pressure Units
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1.1