Fluid MechanicsWEEK 01

Navapadol Kittiamornkul

Outline

- Chapter 1 Fluid properties 1.1 Introduction1.2 Unit System1.3 Changing Unit1.4 Force and Weight1.5 Basic Fluid Properties1.6 Viscosity1.7 Gas Equation1.8 Bulk Modulus1.9 Surface Tension

Outline

- Chapter 2 Static Fluid 2.1 Introduction2.2 Pascal’s Law2.3 Pressure depends on depth2.4 Pressure2.5 Pressure measurement2.6 Force reacts with planar object in fluid2.7 Force reacts with curve object in fluid2.8 Buoyant Force

Outline

- Chapter 3 Fluid Kinematics 3.1 Introduction3.2 Flow Rate and average velocity3.3 Equation of continuity3.4 Energy Equation3.5 Flow Power3.6 Momentum Equation3.7 Internal Flow3.8 Flow measurement

Mark ratio

Mid term examination => 30%=> 1.1 – 2.4

Final examination => 40%=> 2.5 – 3.8

Class mark => 30%=> Assignment=> Attention=> Homework

Chapter 1 Fluid Properties

Fluid => Material that has constant mass, but uncertainty size and shape

=> Size and Shape depend on its container

=> Liquid and Gas

1.1 Introduction

Mechanics=> Branch of science concerned with the behavior of physical body

=> Subjected to force or displacement and subsequenteffects of the body on their environment

Fluid mechanics

=> the branch of physics that studies fluids (liquids, gases, and plasmas) and the forces on them.

=> It can be divided into 3 branches

- Fluid statics

- Fluid Kinematics

- Hydrodynamics

Fluid Statics => The study of fluids at rest

=> Ex. Oil in tank, water in pool

Fluid Kinematics => The study of fluids in motion=> Concern only velocity, acceleration and

displacement=> No force and energy consideration=> Ex. Direction of fluid flow

Hydrodynamics => The study of the effect of forces on fluid motion=> Ex. Water pressure on pipe

1.2 Unit System

Unit in Fluid Mechanics => International System of Units (S.I. Units)

The Symbol of unit => Dimensions=> Divided into 2 types

- Primary dimensions- One variable - Ex. L = Length, M = Mass, T = Time

- Secondary dimensions => - Relation of variables- Ex. MLT-2 = Force, LT-1= velocity

LT-2 = acceleration

Amount Dimensions S.I. Units Symbol

Length L Meter m

Mass M Kilogram kg

Time T Second s

Primary Unit of Fluid Mechanics

Amount Dimensions S.I. Units Symbol

Force MLT-2 Newton N, kg•m/s2

Velocity LT-1 Meter/second m/s

Acceleration LT-2 Meter/second2 m/s2

Area L2 Square meter m2

Flow rate L3T-1 Cubic meter/second m3/s

Pressure ML-1T-2 Pascal Pa, N/m2

Density ML-3 Kilogram/cubic meter Kg/m3

Specific Weight ML-2T-2 Newton/cubic meter N/m3

Dynamic viscosity ML-1T-1 Pascal•second Pa•s

Power ML2T-3 Watt W

Secondary Unit of Fluid Mechanics

Prefixes => Symbol of multiplier for large and small number before units

EX. How to write 19,000,000 m in prefix symbol?

1.3 Changing Unit

1. Use prefixes to change unit in the same unit system

Ex. 1. Change 3,462 m to km

Ex. 2. Change 6MN to N

Ex. 3. Change 216 MW to GW

Ex. 4. Change 34,423,001 J to MJ

****“It can only change at the same amount.” ****

2. change between unit system

Ex. 1. Change 5 cm to in (when 2.54 cm = 1 in)

Ex. 2. Change 30 s to min (when 1 min = 60 s)

Ex. 3. Change 20 s to hr (when 1 hr = 3600 s)

1.4 Force and Weight

Force => any influence that causes an object to undergo a certain change, either concerning its movement, direction, or geometrical construction. In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest)

F = ma ; m = mass (kg)

a = acceleration (m/s2)

F = force (kg•m/s2 = N)

Weight => Kind of force that is caused by gravity of earth

W = mg ; m = mass (kg)

a = earth gravity = 9.8 (m/s2)

F = force (kg•m/s2 = N)

EX. A space ship has 9000 N on earth. When it travels to the moon whichhas gravity 1 in 5 of the earth. Find

A. mass of space ship on the earth and moon

B. weight of space ship on the moon