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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