Welcome to Level 2BEng (Hons)/MEng Civil Engineering

Fluid Mechanics(UBLLCN-20-2)

Dr. Roshan Suminda Ranasinghe

Northshore College of Business & Technology

23rd January 2013

Module content

SECTION A: fundamentals

1. Statics: General properties of fluids, hydrostatic pressure, buoyancy, pressures and measurement, forces on submerged surfaces, stability of floating bodies.

2. Basic Concepts of Fluid Motion: Flow of water, types of flow, stream lines, flow nets, drag.

3. Two Dimensional Inviscid Flow: Conservation equations, continuity, Euler and Bernouilli equations, kinematics of fluid motion, velocity, acceleration, streamlines, streamtubes, particle paths, definition of rotational and irrotational flow.

4. Dynamics: Laminar and turbulent flows, Reynold's number, fluid acceleration, energy equation, momentum equation, flow around a cylinder, pressure distribution, flow around aerofoils and vanes.

5. An introduction to Viscous Flow.6. An introduction to Particle Mechanics.

Module content

SECTIONB: Applications

1. Steady Flow in Pipes: The Darcy-Weisbach formula, relationship between friction factor, Reynolds number and relative roughness. The design of complete pipe systems involving energy changes as well as friction losses, analysis of pipe networks, iterative solutions.

2. Steady Flows in Open Channels: The use and limitations of power formulae (Chezy, Manning), uniform flow, conservation equations of energy and force/momentum for non uniform flow, the hydraulic jump, flow through flumes and over weirs.

3. Dimensional Analysis: principles, dimensionless groups, economy in presentation of data, dynamic similarity, experimental verification.

4. Selection of Criteria: Parameters and scales for models of rivers, coasts, harbours and hydraulic structures.

5. Unsteady Pipe Flow: Compressibility waves, water hammer, surge tanks.

6. Machines: The use and characteristics of roto-dynamic pumps and turbines, pump loads.

By the time you have completed this module you should be able to :

1. Explain basic concepts of fluid flow.2. Derive logical equations for fluid flow.3. Calculate pressures and loads imposed by static and moving fluids.4. Discuss the use of model testing to predict prototype behaviour.5. Recognise the limitations of design methods and CAD software.6. Design pipe and open channel systems.7. Determine water levels and flows in channels.8. Assess water resources and river flows qualitatively.9. Apply standard design methods and computer software.

Learning outcomes

Lectures: 33 hours (22 sessions of 1.5 hours)

Lab: 18 hours (06 classes)Feedback sessions: 18 hours (06 sessions of 3

hours)Directed learning: 30 hours (06 worksheets of 5

hours)Self-directed learning: 80 hours (reading, revising, extra

time on worksheets)Summative Assessment: 21 hours

Total study hours: 200 hours = 20 credits

Workload

Formative06 worksheets

Summative

Assessment

COMPONENT WEIGHTING DATE

A: Examination (3hr) 70% August 2013

B: Coursework (lab experiments) 30%

Lecture 1: Introduction to Fluid Mechanics

What is a Fluid?

A fluid is a substance, which deforms continuously under the action of “shearing forces”.

9

Introduction

A solid undergoes definite displacement (or breaks completely) when subjected to shearing forces

10

Newton’s Law of Viscosity

Experiments show that when other quantities are heldconstant, F is directly proportional to A and to the velocity gradient, u/y. Thus:

The ratio u/y, may also be expressed as du/dy. Thus:

Shear stress,

A

Fτ

y

uF

AF

y

uAF

dy

duμτ

11

Rheological Classification of Fluids

Variation of shear stress with velocity gradient.

12

Liquids and Gases

13

Properties of Fluids

1. Density

2. Viscosity

V

mρ

dy

duμτ

Dynamic viscosity coefficient =

Kinematic viscosity coefficient =ρ

μν

μ

14

Properties of Fluids…

3. Surface Tension

4. Capillarity

The force due to internal pressure =

Force due to surface tension around perimeter =

For equilibrium,=

2. rπp

rπσ 2.

rσp

rπσrπp

/2

2.2

Weight of fluid column raised/lowered =

Upward pull due to surface tension =

For equilibrium ,

Capillary rise,

gρHrπ .2

rπθσ 2.cos

gρHrπrπθσ 22.cos

grρθσH /cos2