High Lift Devices
주요명칭 동체 Flap 수직날개 Vertical Wing Rudder Elevator 수평날개
방향전환 () Rolling Yawing Pitching
방향전환 () Rolling Yawing Pitching
Potential Flow of Helicopter PNU ME CFD LAB. =0 o =60 o =90 o =0 o =50o
헬리콥터비행원리 ()
헬리콥터비행원리 ()
Cobra Bell 끄루크
부메랑의원리 양력감소 양력증가
부메랑 (Boomerang) 형광부메랑
새와비행기의날개 새날개 곤충날개 박쥐날개
Sketch by Leonardo da Vinci
Leonardo da Vinci & Michelangelo Leonardo da Vinci (45-59) Michelangelo di Lodovico Buonarroti Simoni (475-564)
Works by Michelangelo 천지창조 (50)
Works by Michelangelo 아담의창조이브의창조
Works by Michelangelo 최후의심판 (Hymns of Advent) 537-54 다윗상 David(50-504)
designed by Michelangelo
Works by Leonardo da Vinci (45-59) Mona Lisa (503 505/507) Virgin and Child(487?)
Works by Leonardo da Vinci (45-59) The Last Supper (498) da Vinci Code
Leonardo da Vinci Helicopter Airplane
Leonardo da Vinci Tank Automobile Parachute Machine Gun
Leonardo da Vinci
Leonardo da Vinci
Leonardo da Vinci
날개이론의응용 ()
날개이론의응용 () 수중익선
골프공의원리 항력증가, 비행거리감소 항력감소, 비행거리증가
수영의원리 () 부력 항력증가 항력감소
수영의원리 ()
수영의원리 (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. 3.0 P decreases as z increases. Gage Pressure
3.6.3 Flowrate Measurement - Bernoulli Eq : - Continuity Eq : p V p V V Subst. A V A
- Volume Flow Rate : - Therefore, for a given flow geometry (A and A) the flow rate can be determined if the pressure difference, pp-p, is measured. A A p p V
Ex. 3. - Bernoulli : p V p V - Continuity : A V V A
Sluice Gate: Assume that the velocity profiles are uniform sufficiently upstream and downstream of the gate. - Bernoulli : p V z p V z 0 0 - Continuity : Hence, Q z Q Or, b A V AV bz g V bzv z z z z
- In the limit of, z z gz b z z z gz b z z z z z z z z g b z z z z z g b z Q z z z z z z g b z Q
- 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 z z z is approximately V. gz z z - Because the fluid can not turn a sharp 90 o corner, the phenomena of vena contracta is generated and z a. - The coefficient of contraction, C c =z /a, is typically 0.6 for a/z <0..
Ex. 3. Z = a=
Weir : We would expect the average velocity across the top of the weir to be proportional to. gh Q C 3 / A gh CHb gh Cb gh where C is constant, determined by the experiment.
Ex. 3.3
3.7 The Energy Line and the Hydraulic Grade Line For steady, inviscid, incompressible flow the total energy remains constant along a streamline. V g Velocity Head p Pressure Head PiezometerHead z H constant on a streamline Elevation Head Total Head - 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: dp V gz const. p V If the fluid is incompressible z constant along streamline - If assuming that the flow is isothermal along the streamline, dp V gz prt Tconst dp p / RT RT dp p V V gz gz const Thus, V g z RT p ln g p V g z
- If assuming that the flow is isentropic of a perfect gas, const gz V dp p C gz V dp p p k / /k p C k / k / const gz V p k C k k / / / const gz V p k k C k / k / const gz V p k k p k / k / k const gz V p k k gz V p k k gz V p k k Thus,
Incompressible 0.3 V = 335 ft/sec = 8mph = 0m/s = 367km/h.
Unsteady Effects: Return to F=ma along the streamline F s sin dz / ds p Vol s ( Vol) a s Thus, a s ds dp dz 0 By the way, since a s dv(t,s) dt V t t t V s s t V t V V s Therefore, V V ds dp d t s V dz 0 p V z ds p V z s t (along a streamline in the incompressible inviscid flows)
Ex. 3.6 p s s V z V ds p t V z
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: p V gz const. Potential Energy Pressure Energy ude toflow work. Actsas potential -like energy.because high pressure is similar to high elevation in the concept of potential. KineticEnergy (h L :head loss) (For inviscid Flow) p p V V gz gz p E in mechanical energy input V p gz V gh L energy loss due to the viscouseffects gz gh L (For viscous Flow)