Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 53 views

    Chapter 1 - Part A

    Uploaded by

    Qiang Lo
    This document provides an overview of fluid mechanics. It defines fluid mechanics as the science dealing with fluids at rest or in motion, and their interactions with surfaces. Key topics covered include: - The definitions and differences between liquids, gases, and solids - Common fluid properties like density, pressure, viscosity - Applications of fluid mechanics in various engineering fields like aerodynamics, hydraulics, piping systems - Systems of units used to quantify fluid properties and equations - The concept of an ideal gas and when real gases can be approximated as ideal

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Chapter 1 - Part A

    Uploaded by

    Qiang Lo
    53 views30 pages
    This document provides an overview of fluid mechanics. It defines fluid mechanics as the science dealing with fluids at rest or in motion, and their interactions with surfaces. Key topics covered include: - The definitions and differences between liquids, gases, and solids - Common fluid properties like density, pressure, viscosity - Applications of fluid mechanics in various engineering fields like aerodynamics, hydraulics, piping systems - Systems of units used to quantify fluid properties and equations - The concept of an ideal gas and when real gases can be approximated as ideal

    Original Description:

    o0oo

    Original Title

    Chapter 1_Part A

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    This document provides an overview of fluid mechanics. It defines fluid mechanics as the science dealing with fluids at rest or in motion, and their interactions with surfaces. Key topics covered include: - The definitions and differences between liquids, gases, and solids - Common fluid properties like density, pressure, viscosity - Applications of fluid mechanics in various engineering fields like aerodynamics, hydraulics, piping systems - Systems of units used to quantify fluid properties and equations - The concept of an ideal gas and when real gases can be approximated as ideal

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    53 views30 pages

    Chapter 1 - Part A

    Uploaded by

    Qiang Lo
    This document provides an overview of fluid mechanics. It defines fluid mechanics as the science dealing with fluids at rest or in motion, and their interactions with surfaces. Key topics covered include: - The definitions and differences between liquids, gases, and solids - Common fluid properties like density, pressure, viscosity - Applications of fluid mechanics in various engineering fields like aerodynamics, hydraulics, piping systems - Systems of units used to quantify fluid properties and equations - The concept of an ideal gas and when real gases can be approximated as ideal

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 30

    FLUID MECHANICS 1

    CHAPTER 1:
    BASIC PRINCIPLES OF FLUID

    PRESENTATION OUTLINE

    Introduction to fluid
    mechanics.
    Applications of fluid
    mechanics
    Dimension, Dimensional
    Homogeneity and Units
    System of units
    Properties of fluid

    Learning Objective
    After completing this chapter, student should be able to:1. Determine the dimensions and units of physical
    2. Identify the key fluid properties used in the analysis
    of fluid behaviour
    3. Calculate common fluid properties given given
    appropriate information
    4. Explain of fluid properties

    Introduction
    Mechanics: The oldest physical science that
    deals with both stationary and moving bodies
    under the influence of forces.
    Statics: The branch of mechanics that
    deals with bodies at rest.
    Dynamics: The branch that deals with
    bodies in motion.
    Fluid mechanics: The science that deals with
    the behavior of fluids at rest (fluid statics) or in
    motion (fluid dynamics), and the interaction of
    fluids with solids or other fluids at the
    boundaries.
    Fluid dynamics: Fluid mechanics is also
    referred to as fluid dynamics by considering
    fluids at rest as a special case of motion with
    zero velocity.

    Fluid mechanics deals with


    liquids and gases in motion or
    at rest.

    Hydrodynamics: The study of the motion of fluids that can be


    approximated as incompressible (such as liquids, especially water,
    and gases at low speeds).
    Hydraulics: A subcategory of hydrodynamics, which deals with
    liquid flows in pipes and open channels.
    Gas dynamics: Deals with the flow of fluids that undergo
    significant density changes, such as the flow of gases through
    nozzles at high speeds.
    Aerodynamics: Deals with the flow of gases (especially air) over
    bodies such as aircraft, rockets, and automobiles at high or low
    speeds.
    Meteorology, oceanography, and hydrology: Deal with naturally
    occurring flows.

    What is a Fluid?
    Fluid: A substance in the liquid or gas
    phase.
    A solid can resist an applied shear
    stress by deforming.
    A fluid deforms continuously under the
    influence of a shear stress, no matter
    how small.
    In solids, stress is proportional to
    strain, but in fluids, stress is
    proportional to strain rate.
    When a constant shear force is
    applied, a solid eventually stops
    deforming at some fixed strain angle,
    whereas a fluid never stops deforming
    and approaches a constant rate of
    strain.

    Deformation of a rubber block


    placed between two parallel plates
    under the influence of a shear force.
    The shear stress shown is that on
    the rubberan equal but opposite
    shear stress acts on the upper plate.

    Stress: Force per unit area.


    Normal stress: The normal
    component of a force acting on a
    surface per unit area.
    Shear stress: The tangential
    component of a force acting on a
    surface per unit area.
    Pressure: The normal stress in a
    fluid at rest.
    Zero shear stress: A fluid at rest is
    at a state of zero shear stress.
    When the walls are removed or a
    liquid container is tilted, a shear
    develops as the liquid moves to
    re-establish a horizontal free
    surface.

    The normal stress and shear stress


    at the surface of a fluid element.
    For fluids at rest, the shear stress is
    zero and pressure is the only
    normal stress.

    In a liquid, groups of molecules can move relative to each other,


    but the volume remains relatively constant because of the strong
    cohesive forces between the molecules. As a result, a liquid
    takes the shape of the container it is in, and it forms a free
    surface in a larger container in a gravitational field.
    A gas expands until it encounters the walls of the container and
    fills the entire available space. This is because the gas
    molecules are widely spaced, and the cohesive forces between
    them are very small. Unlike liquids, a gas in an open container
    cannot form a free surface.

    Unlike a liquid, a gas does not


    form a free surface, and it
    expands to fill the entire
    available space.

    Intermolecular bonds are strongest in solids and weakest in gases.


    Solid: The molecules in a solid are arranged in a pattern that is
    repeated throughout.
    Liquid: In liquids molecules can rotate and translate freely.
    Gas: In the gas phase, the molecules are far apart from each other, and
    molecular ordering is nonexistent.

    The arrangement of atoms in different phases: (a) molecules are at relatively


    fixed positions in a solid, (b) groups of molecules move about each other in
    the liquid phase, and (c) individual molecules move about at random in the
    gas phase.

    Application Areas of Fluid Mechanics

    Power Plant

    Fluid dynamics is used extensively


    in the design of artificial hearts.
    Shown here is the Penn State
    Electric Total Artificial Heart.

    Natural flows

    Boats
    Human Body

    Aircrafts
    Cars

    Wind Turbines

    Industrial Applications

    Piping and Plumbing system

    Dimensions, Dimensional Homogeneity


    and Units
    Fluid mechanics will be
    dealing with a variety of
    fluid characteristics.
    It is necessary to develop
    a system for describing
    these characteristics :Quantitatively
    Qualitatively

    QUANTITATIVELY :
    Aspect serves to identify the nature of fluid
    such as length, time, stress and velocity.
    QUALITATIVELY :
    Aspect provides a numerical measure of the
    characteristic. Quantitative requires both a
    number and a standard. Such standards are
    called unit.

    Primary quantity :
    L : Length
    T : Time
    M : Mass
    : Temperature
    Secondary quantity :
    2
    L : Area
    -1
    LT : Velocity
    -3
    ML : Density

    Example :
    V =Vo + at
    Where V is a uniformly acceleration body

    1
    1
    2
    LT
    = LT
    + LT T
    All theoretically derived equations are dimensionally
    homogeneous. The dimension of the left side of the
    equation must be the same as those on the right side,
    and all additive separate terms must have the same
    dimensions.

    UNIT
    3 major systems that are commonly used in engineering.
    1. British Gravitational (BG) System :
    Length Foot (ft)
    Time second (s)
    Force pound (lb) Temperature Fahrenheit (oF)
    2. International System (SI)
    Length meter (m)
    Time second (s)
    Mass kilogram (kg)
    Temperature Kelvin (K)
    The relation of Kelvin and Celsius is; K = C + 273.15

    3. English Engineering (EE) System :


    Length foot (ft)
    Time second (s)
    Mass pound mass (lbm)
    Force pound (lb or lbf)
    Temperature Rankine (oR)

    Activity 1.1
    A liquid flows through an orifice located
    in the side of a tank as shown on the
    right side. A commonly used the
    equation for determining the volume
    rate of flow, Q through the orifice is
    Q = 0.61A2gh
    gE01_01a(

    where, A is the area, g is the


    acceleration and h is the height of
    liquid

    gE01_01b(

    Dimension of various terms:Q = volume/time = L3T-1


    A = Area = L2
    g = acceleration of gravity = LT-2
    h = Height = L
    L3T-1 = (0.61)(L2)(2)(LT-2)1/2(L)1/2
    L3T-1 = (0.61)(2) (L3T-1)

    Properties of Fluids
    Density

    Density is mass per unit volume;

    Specific volume
    Specific volume is
    volume per unit
    mass

    Typical values at atmospheric condition;

    Water = 1000 kgm-3

    Mercury = 13546 kgm-3

    Air = 1.23 kgm-3

    Paraffin Oil = 800 kgm-3

    g01_02'

    Density of water as a function of temperature

    Specific Weight
    The weight of a unit volume of a substance

    Specific of Gravity
    Defined as the ratio of the density of the
    fluid to the density of water at some
    specified temperature

    Density of water (H2O) = 1000 kg/m

    Density!
    Ideal-gas equation of state: The simplest and bestknown equation of state for substances in the gas
    phase.

    Ru: The universal gas constant

    The thermodynamic temperature scale in the SI is the Kelvin scale.


    In the English system, it is the Rankine scale.

    An ideal gas is a hypothetical substance


    that obeys the relation Pv = RT.
    The ideal-gas relation closely
    approximates the P-v-T behavior of real
    gases at low densities.
    At low pressures and high temperatures,
    the density of a gas decreases and the gas
    behaves like an ideal gas.

    Air behaves as an ideal gas, even at


    very high speeds. In this schlieren
    image, a bullet traveling at about the
    speed of sound bursts through both
    sides of a balloon, forming two
    expanding shock waves. The
    turbulent wake of the bullet is also
    visible.

    In the range of practical interest, many


    familiar gases such as air, nitrogen,
    oxygen, hydrogen, helium, argon, neon,
    and krypton and even heavier gases such
    as carbon dioxide can be treated as ideal
    gases with negligible error.
    Dense gases such as water vapor in steam
    power plants and refrigerant vapor in
    refrigerators, however, should not be
    treated as ideal gases since they usually
    exist at a state near saturation.
    9

    Summary of lessons

    You might also like