High Lift Devices

주요 명칭

동체

수직날개

Vertical Wing

수평날개

Rudder

Elevator

Flap

방향전환(1)

Rolling

Yawing

Pitching

방향전환(2)

Rolling

Yawing

Pitching

PNU ME CFD LAB.

Potential Flow of Helicopter

=0o =60o

=90o =120o =150o

헬리콥터 비행원리(1)

헬리콥터 비행원리(2)

Cobra

Bell

끄루크

부메랑의 원리

양력증가

양력감소

부메랑 (Boomerang)

형광부메랑

새와 비행기의 날개

새 날개

곤충 날개

박쥐 날개

Sketch by Leonardo da Vinci

Leonardo da Vinci (1452-1519)

Michelangelo di Lodovico Buonarroti Simoni

(1475-1564)

Leonardo da Vinci & Michelangelo

Works by Michelangelo

천지창조(1510)

아담의 창조이브의 창조

Works by Michelangelo

Works by Michelangelo

최후의 심판(Hymns of Advent) 1537-1541다윗상

David(1501-1504)

designed byMichelangelo

Works by Leonardo da Vinci (1452-1519)

Mona Lisa (1503–1505/1507) Virgin and Child(1487?)

Works by Leonardo da Vinci (1452-1519)

The Last Supper (1498)

“da Vinci Code”

Leonardo da Vinci

Airplane

Helicopter

Automobile

Tank

Parachute

Machine Gun

Leonardo da Vinci

Leonardo da Vinci

Leonardo da Vinci

Leonardo da Vinci

날개이론의 응용(1)

날개이론의 응용(2)

수중 익선

골프공의 원리

항력증가, 비행거리 감소 항력감소, 비행거리 증가

수영의 원리(1)

부력

항력 증가

항력 감소

수영의 원리(2)

수영의 원리(3)

항력증가 항력감소

For flows of liquids, the severe decrease in pressure may

result in cavitation, when the liquid pressure is reduced to the

vapor pressure.

The cavitation is a cause of severe noise and vibration, and

erosion on the propeller surface.

Ex. 3.10

Gage Pressure

P2 decreases as z2 increases.

3.6.3 Flowrate Measurement

- Bernoulli Eq :

- Continuity Eq :

2

22

2

11 V2

1pV

2

1p

2

1

21 V

A

AV

Subst.

- Volume Flow Rate :

- Therefore, for a given flow geometry (A1 and A2) the flow

rate can be determined if the pressure difference, pp1-p2,

is measured.

2

12

212

1

2

AA

ppV

Ex. 3.11

2

22

2

11 V2

1pV

2

1p

2

1

21 V

A

AV

- Bernoulli :

- Continuity :

Sluice Gate:

Assume that the velocity profiles are uniform sufficiently

upstream and downstream of the gate.

- Bernoulli :

- Continuity :

Or,

Hence,

2

2

2

0

21

2

1

0

1 zV2

1pzV

2

1p

2211 VAVAQ

2211 VbzVbz

2

12

212

zz1

zzg2bzQ

- In the limit of ,21 zz

12

21

2

12

2121

2

12122

12

212

2

22

1

2

21

gzbz

zz

gzbz

zzzz

zzzgbz

zz

zzgbzQ

zz

2

12

212

zz1

zzg2bzQ

- This limiting result represents the fact that if ,

the kinetic energy of the fluid upstream of the gate is

negligible and the fluid velocity after it has fallen a distance

is approximately .

- Because the fluid can not turn a sharp 90o corner, the

phenomena of vena contracta is generated and z1a.

- The coefficient of contraction, Cc=z2/a, is typically 0.62 for

a/z1<0.2.

21 zz

121 zzz 12 gz2V

Ex. 3.12

Z1=

a=

Weir :

We would expect the average velocity across the top of the

weir to be proportional to . gH2

2/3

111 Hg2bCgH2HbCgH2ACQ

where C1 is constant, determined by the experiment.

Ex. 3.13

3.7 The Energy Line and the Hydraulic Grade Line

For steady, inviscid, incompressible flow the total energy remains

constant along a streamline.

streamline aon constant Hz

p

g2

V

HeadTotal

Head Piezometer

HeadElevation

HeadPressure

HeadVelocity

2

- The difference between

the energy line (EL) and the

hydraulic grade line (HGL)

is the velocity head.

3.8 Restriction on Use of the Bernoulli Equation

Compressibility Effects:

- If assuming that the flow is isothermal along the streamline,

.constgzV2

1dp 2

streamline alongconstant zV2

1p 2

If the fluid is incompressible

constgzV2

1

p

dpRT

gzV2

1

RT/p

dp gzV

2

1dp

2

constT

2

RTp

2

2

2

2

2

11

2

1 zg2

V

p

pln

g

RTz

g2

V

Thus,

- If assuming that the flow is isentropic of a perfect gas,

constgzV2

1dppC gzV

2

1dp 2p

p

k/11/k

pC

2 2

1k/1k/1

constgzV

pk

C kk

21/1

1 21/1/1

constgz2

Vp

1k

kC

2k/11k/1

constgz2

Vp

1k

kp 2k/11

k/1

k

constgz2

Vp

1k

k 2

2

2

2

2

21

2

1

1

1 gz2

Vp

1k

kgz

2

Vp

1k

k

Thus,

0.3

Incompressible

V = 335 ft/sec

= 228mph

= 102m/s

= 367km/h.

Unsteady Effects:

Return to F=ma along the streamline

Thus,

By the way, since

s

ds/dz

s a)Vol(Vols

psinF

0dzdpdsa s

s

VV

t

V

t

s

s

V

t

t

t

V

dt

)s,t(dVa s

0dz2

Vddpds

t

V 2

Therefore,

2

2

22

s

s1

2

11 zV2

1pds

t

VzV

2

1p

2

1

(along a streamline in the incompressible inviscid flows)

Ex. 3.16

2

2

22

s

s

1

2

11

zV2

1pds

t

V

zV2

1p

2

1

Rotational Effects:

- Another restriction of the Bernoulli equation is that it is only

applicable along the streamline.

- In general, the Bernoulli constant varies from streamline to

streamline.

- However, under certain restrictions this constant is the same

throughout the entire flow field

“Irrotational” Flow Field

Viscous Effects:

const.gzV

2

1p

Energy PotentialEnergy Kinetic

2

potential. ofconcept in theelevation high similar to is pressure

high Because energy. like-potential as Acts

work.flow toudeEnergy Pressure

(For inviscid Flow)

effects viscous the todue

lossenergy

L2

2

2

2

21

2

1

1

1 ghgzV2

1pgzV

2

1p

(hL:head loss)

(For viscous Flow)

L2

2

2

2

2

inputenergy mechanical

in1

2

1

1

1 ghgzV2

1pEgzV

2

1p