Aeronautical Engineer Data Book Episode 5 doc

73 Aeronautical definitions Table 4.4 Continued ACARS AD ADF AFIS AFTT AP APU ASI ATIS AWOS C of A C/R CAS CHT COM CONV/MOD DG DME EFIS EGT ELT ENC F/D FADEC FB

Trang 1

71 Aeronautical definitions

4.3 Helicopter terminology

Table 4.3 Helicopter terminology and acronyms

Trang 2

72 Aeronautical Engineer’s Data Book

Table 4.3 Continued

4.4 Common aviation terms Table 4.4 Aviation acronyms

3/LMB 3 Light Marker Beacon 360CH 360 Channel Radio

720CH 720 Channel Radio

AC or AIR Air Conditioning

Trang 3

ACARS

AD

ADF

AFIS

AFTT

AP

APU

ASI

ATIS

AWOS

C of A

C/R

CAS

CHT

COM

CONV/MOD

DG

DME

EFIS

EGT

ELT

ENC

F/D

FADEC

FBO

FMS

G/S

G/W

GPS

GPWS

GS

HF

HSI

HUD

IAS

ICE

IFR

ILS

KCAS

KIAS

Aircraft Communication Addressing and Reporting System

Airworthiness Directive

Automatic Direction Finder

Airborne Flight Info System

Air Frame Total Time (in hours) Autopilot

Auxiliary Power Unit

Air Speed Indicator

Automatic Terminal Information Service (a continuous broadcast of recorded non-control information in selected high activity terminal areas)

Automatic Weather Observation Service Certificate of Airworthiness

Counter Rotation (propellers)

Calibrated Air Speed

Cylinder Head Temperature Gauge Com Radio

Conversion/Modification (to aircraft) Directional Gyro

Distance Measuring Equipment

Electronic Flight Instrument System Exhaust Gas Temperature Gauge Emergency Locator Transmitter

Air Traffic Control Encoder

Flight Director

Full Authority Digital Engine Control Fixed Base Operation

Flight Management System

Glideslope

Gross Weight

Global Positioning System

Ground Proximity Warning System Ground Speed

High Frequency Radio

Horizontal Situation Indicator

Head Up Display

Indicated Air Speed

Has Anti-Icing Equipment

Instrument Flight Rules

Instrument Landing System

Calibrated air speed (Knots)

Indicated air speed (Knots)

KNOWN ICE Certified to fly in known icing conditions LOC Localizer

LRF Long Range Fuel

MLS Microwave Landing System

N/C Navigation and Communication Radios NAV Nav Radio

Trang 4

NAV/COM

NDH

NOTAM

O/H

OAT

OC

OMEGA

PANTS

PTT

RALT

RDR

RMI

RNAV

RSTOL

SB

SFRM

SHS

SLC

SMOH

SPOH

STOH

STOL

STORM

T/O

TAS

TBO

TCAD

TCAS

TREV

TT

TTSN

TWEB

TXP

Va

Vfe

VFR

Vle

VNAV

Vne

Vno

VOR

Vs

VSI

Vso

Vx

Vy

XPDR

Navigation and Communication Radios

No Damage History

Notice to Airmen (radio term)

Overhaul

Outside Air Temperature

On Condition

VLF (Very Low Frequency) Navigation Fixed Gear Wheel Covers

Push to Talk

Radar Altimeter

Radar

Radio Magnetic Indicator

Area Navigation (usually includes DME) Roberson STOL Kit

Service Bulletin

(Time) Since Factory Remanufactured Overhaul

Since Hot Section

Slaved Compass

Since Major Overhaul

Since Propeller Overhaul

Since Top Overhaul

Short Takeoff and Landing Equipment Stormscope

Takeoff (weight)

True Air Speed

Time Between Overhauls

Traffic/Collision Avoidance Device Traffic Alert and Collision Avoidance System

Thrust Reversers

Total Time

Time Since New

Transcribed Weather Broadcast Transponder

Safe operating speed

Safe operating speed (flaps extended) Visual Flight Rules

Safe operating speed (landing gear extended)

Vertical Navigation computer

‘Never exceed’ speed

Maximum cruising ‘normal operation’ speed

Very High Frequency Omnidirectional Rangefinder

Stalling speed

Vertical Speed Indicator

Stalling speed in landing configuration Speed for best angle of climb

Speed for best rate of climb

Transponder

Trang 5

4.5 Airspace terms

The following abbreviations are in use to describe various categories of airspace

Table 4.5 Airspace acronyms

AAL

AGL

AIAA

AMSL

CTA

CTZ

FIR

FL

LFA

MATZ

MEDA

Min DH

SRA

SRZ

TMA

Above airfield level

Above ground level

Area of intense air activity

Above mean sea level

Control area

Control zone

Flight information region

Flight level

Local flying area

Military airfield traffic zone (UK)

Military engineering division airfield (UK) Minimum descent height

Special rules airspace (area)

Special rules zone

Terminal control area

Trang 6

Section 5

Basic fluid mechanics

5.1 Basic poperties

5.1.1 Basic relationships

Fluids are divided into liquids, which are virtually incompressible, and gases, which are compress ible A fluid consists of a collection of molecules

in constant motion; a liquid adopts the shape of a vessel containing it whilst a gas expands to fill any container in which it is placed Some basic fluid relationships are given in Table 5.1

Table 5.1 Basic fluid relationships

Density ( ) Mass per unit volume

Units kg/m 3 (lb/in 3 )

Specific gravity (s) Ratio of density to that of

water, i.e s = / water

Specific volume (v) Reciprocal of density, i.e s =

1/ Units m 3 /kg (in 3 /lb) Dynamic viscosity () A force per unit area or shear

stress of a fluid Units Ns/m 2

(lbf.s/ft 2 ) Kinematic viscosity ( ) A ratio of dynamic viscosity to

density, i.e = µ/ Units m2 /s (ft 2 /sec)

5.1.2 Perfect gas

A perfect (or ‘ideal’) gas is one which follows

Boyle’s/Charles’ law pv = RT where:

p = pressure of the gas

v = specific volume

T = absolute temperature

R = the universal gas constant

Although no actual gases follow this law totally, the behaviour of most gases at temperatures

Trang 7

77 Basic fluid mechanics

well above their liquefication temperature will

approximate to it and so they can be considered

as a perfect gas

5.1.3 Changes of state

When a perfect gas changes state its behaviour approximates to:

pv n = constant

where n is known as the polytropic exponent

Figure 5.1 shows the four main changes of state relevant to aeronautics: isothermal, adiabatic: polytropic and isobaric

Specific volume, v

Isobaric

n = ∞

n = κ

n = 1

n = 0

1<n< κ

Polytropic Adiabatic

Isothermal

0

Fig 5.1 Changes of state of a perfect gas

5.1.4 Compressibility

The extent to which a fluid can be compressed in volume is expressed using the compressibility coefficient

∆v/v

=

∆p

1

where ∆v = change in volume

v = initial volume

∆p = change in pressure

K = bulk modulus

Trang 8

�

Also:

∆ = dp

d and

a = �� d = �

K

p

d

where a = the velocity of propagation of a

pressure wave in the fluid

5.1.5 Fluid statics

Fluid statics is the study of fluids which are at rest (i.e not flowing) relative to the vessel containing

it Pressure has four important characteristics:

• Pressure applied to a fluid in a closed vessel (such as a hydraulic ram) is transmitted to all parts of the closed vessel at the same value (Pascal’s law)

• The magnitude of pressure force acting at any point in a static fluid is the same, irrespective of direction

• Pressure force always acts perpendicular to the boundary containing it

• The pressure ‘inside’ a liquid increases in proportion to its depth

Other important static pressure equations are:

• Absolute pressure = gauge pressure + atmospheric pressure

• Pressure (p) at depth (h) in a liquid is given

by p = gh

• A general equation for a fluid at rest is

pdA – p + dp

dz dA – gdAdz = 0

This relates to an infinitesimal vertical cylinder of fluid

5.2 Flow equations

Flow of a fluid may be one dimensional (1D), two dimensional (2D) or three dimensional

Trang 9

The stream tube for conservation of mass

1

2

p1

p2

s

z

δs δs

dp ds

The stream tube and element for the momentum equation

W The forces on the element

F

pA

δs

W

ds

(p+dds p δs) (A+δA)

δs)

2

Control volume for the energy equation

s

1

2

z1

v 2 p2

T2p 2

v1p1

T 1 p1

z2

q

α

Fig 5.2 Stream tube/fluid elements: 1-D flow

(3D) depending on the way that the flow is constrained

5.2.1 1D Flow

1-D flow has a single direction co-ordinate x and

a velocity in that direction of u Flow in a pipe

or tube is generally considered one dimensional

Trang 10

80

Table 5.2 Fluid principles

Conservation of mass Matter (in a stream tube or anywhere else) cannot be

created or destroyed

Conservation of momentum The rate of change of momentum in a given direction =

algebraic sum of the forces acting in that direction (Newton’s second law of motion)

Conservation of energy Energy, heat and work are convertible into each other

and are in balance in a steadily operating system

Equation of state Perfect gas state: p/ T = r and the first law of

thermodynamics

vA = constant dp

� + 1 2 v2+ gz = constant

∫ � p This is Bernoulli’s equation 2

v

c T + p = constant for an adiabatic (no heat 2 transferred) flow system

p = k k = constant

 = ratio of specific heats c p /c v

Trang 11

The equations for 1D flow are derived by considering flow along a straight stream tube (see Figure 5.2) Table 5.2 shows the principles, and their resulting equations

5.2.2 2D Flow

2D flow (as in the space between two parallel flat plates) is that in which all velocities are

parallel to a given plane Either rectangular (x,y)

or polar (r, ) co-ordinates may be used to describe the characteristics of 2D flow Table 5.3 and Figure 5.3 show the fundamental equations

Rectangular co-ordinates

v

u

y

x

u + ∂ ∂ x u δ x 2

v – ∂ ∂ y v δ y

δ x

2

u – ∂ ∂ x u δ x 2

v + ∂ ∂ y v δ y 2

P

Unit thickness

Polar co-ordinates

P(r, θ )

q n + ∂ q n

q n

∂ r

δ r

2

q n – ∂ q n

∂ r

δ r

2

∂ q t

qt

δθ

2

q t +

∂ q t

∂θ

δθ

2

(r–

)δθ

δr

2

(r + )δθ

δr

2

Fig 5.3 The continuity equation basis in 2-D

Trang 12

82

Table 5.3 2D flow: fundamental equations

Laplace’s equation

+ = 0 = ∂ 2 ∂ 2

+ 2

2

∂y

∂x

A flow described by a unique velocity potential is irrotational

∂ 2 ∂ 2

or

∂ 2 ∂ 2

∂y

∂x

2 = + 2 2

∂y

∂x

Equation of motion in 2D

X – ∂p

∂x The principle of force = mass (Newton’s law of motion) applies to fluids acceleration

and fluid particles

∂u

∂t + u

∂u

∂x + v

∂u

∂y =

1

∂v

∂t + u ∂v ∂x + v ∂v ∂t =

1

Y – ∂p

∂y

Trang 13

Equation of continuity in 2D

(incompressible flow)

If fluid velocity increases in the x direction,

= 0 or, in polar

∂u

+ 1 r ∂q t

∂

q n

r +

∂v

∂y

∂q n

∂r

∂v

∂q t

+ ∂r – ∂ 1 ∂q n

=

r

Stream function (incompressible flow) Velocity at a point is given by: is the stream function Lines of constant

∂x

∂y

give the flow pattern of a fluid stream (see Figure 5.5).

∂u

∂y

q t

r

∂y

op

Trang 14

∆m

v

x

y

u

P(x,y)

0

Q(x+ δx,y+δy)

u+ ∂u

∂x δx+ ∂∂y δu y

v+ ∂v

∂x δx+ ∂∂y δv y

Fig 5.4 The vorticity equation basis in 2-D

y

x

u

0

dQ

dy

B

A

dx

v

Fig 5.5 Flow rate (q) and stream function () relationship

δs β β

q sin

β qcos β

q

Fig 5.6 Velocity potential basis

Trang 15

� � �

2

5.2.3 The Navier-Stokes equations

The Navier-Stokes equations are written as:

+u +v =X– +µ� ∂2u

∂x2 + u

∂y

∂2

∂u

∂t

∂u

∂x

∂u

∂y

∂p

∂x

∂v

∂t ∂v ∂x ∂v ∂y ∂p ∂y +µ� 2

2

∂ v

∂x ∂ v ∂y2

=Y–

Inertia Body Pressure Viscous term force term term

term

O

ψ = constant, i.e streamlines radiating from the origin O

φ = constant, i.e equipotential lines centred at the origin O.

x

If q>O this is a source of strength |q|

If q<O this is a sink of strength |q|

Flow due to a combination

ψ = constant

A

y

x

φ = constant

of source and sink

Fig 5.7 Sources, sinks and combination

Trang 16

5.2.4 Sources and sinks

A source is an arrangement where a volume of fluid (+q) flows out evenly from an origin

toward the periphery of an (imaginary) circle

around it If q is negative, such a point is termed

a sink (see Figure 5.7) If a source and sink of

equal strength have their extremities infinitesi mally close to each other, whilst increasing the

strength, this is termed a doublet

5.3 Flow regimes

5.3.1 General descriptions

Flow regimes can be generally described as follows (see Figure 5.8):

Steady Flow parameters at any point do

they may differ between points) Unsteady Flow parameters at any point vary

Laminar Flow which is generally considered flow smooth, i.e not broken up by eddies Turbulent Non-smooth flow in which any

causing eddies and turbulence Transition The condition lying between flow laminar and turbulent flow regimes

5.3.2 Reynolds number

Reynolds number is a dimensionless quantity which determines the nature of flow of fluid over a surface

Inertia forces

Viscous forces

VD VD

where = density

µ = dynamic viscosity

= kinematic viscosity

V = velocity

D = effective diameter

Trang 17

Low Reynolds numbers (below about 2000) result in laminar flow High Reynolds numbers (above about 2300) result in turbulent flow

Basic fluid mechanics 87

‘Wake’ eddies move slower than the rest

of the fluid

Steady flow

Unsteady flow

Boundary layer

Velocity distributions in laminar and turbulent flows

The flow is not steady

relative to any axes

Wake Area of laminar flow

Area of turbulent flow Boundary layer of

thickness ( δ)

Turbulent flow

Laminar flow v

umax

u

The flow is steady, relative

to the axes of the body

Fig 5.8 Flow regimes

Trang 18

Values of Re for 2000 < Re < 2300 are gener

ally considered to result in transition flow Exact flow regimes are difficult to predict in this region

5.4 Boundary layers

5.4.1 Definitions

The boundary layer is the region near a surface

or wall where the movement of the fluid flow

is governed by frictional resistance

The main flow is the region outside the

boundary layer which is not influenced by frictional resistance and can be assumed to be

‘ideal’ fluid flow

Boundary layer thickness: it is convention

to assume that the edge of the boundary layer lies at a point in the flow which has a velocity equal to 99% of the local mainstream velocity

5.4.2 Some boundary layer equations

Figure 5.9 shows boundary layer velocity profiles for dimensional and non-dimensional cases The non-dimensional case is used to allow comparison between boundary layer profiles of different thickness

y

Edge

of BL 0.99 U ∼U1 ∼

∂u

∂y

= y

y

u

Edge

of BL

u = 1.0

δ

U1

Fig 5.9 boundary layer velocity profiles

Trang 19

�

where:

µ = velocity parallel to the surface

y = perpendicular distance from the surface

= boundary layer thickness

U1 = mainstream velocity

u = velocity parameters u/U1(non-dimensional)

y = distance parameter y/ (non-dimensional)

∂y

Boundary layer equations of turbulent flow:

�

∂x

 = µ ∂u�

∂y – �u��v �' �'

�

∂y

∂p

= 0

�

∂y

�

∂x ∂u + ∂ = 0

5.5 Isentropic flow

For flow in a smooth pipe with no abrupt changes of section:

u

dA

A

equation of momentum

k

dp

d

p = c

isentropic relationship

These lead to an equation being derived on the basis of mass continuity:

dp

u

i.e

or

= – M2

d

M2 = du

u

Trang 16

86 Aeronautical Engineer? ??s Data Book. ..

Fig 5. 8 Flow regimes

Trang 18

88 Aeronautical Engineer? ??s Data Book. .. class="text_page_counter">Trang 14

84 Aeronautical Engineer? ??s Data Book

∆m

v

x

Định dạng
Số trang	20
Dung lượng	143,21 KB