Easy summary 150~200word in 3hrs
ksjaw11
aerodynamics.pptxEME1- Aerodynamics
Prof. Seongkyu Lee
Mechanical and Aerospace Engineering
UC Davis
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
What is Aerodynamics?
Aerodynamics = Aero (air) + dynamics (body motion)
It is related to fluid mechanics
It is the study of the properties of moving air, and especially of the interaction between the air and solid bodies moving through it.
Examples:
Airplane
Rocket
Helicopter
Kite
Car
Wind turbine
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Basics of Aircraft Forces
The four forces of flight are lift, weight, thrust and drag.
gravity pulling down on objects
opposite of weight. Everything that flies must have lift
slow something down.
opposite of drag push that moves something forward
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Lift force – wing & airfoil
wing
Airfoil – 2D section of wing
Lift is generated on the wing or airfoil
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Flow over Airfoil
Pressure difference between the lower surface and upper surface
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Bernoulli's principle
Daniel Bernoulli, 1700-1782
The principle in hydrodynamics that an increase in the velocity of a stream of fluid results in a decrease in pressure. Also called Bernoulli effect or Bernoulli theorem.
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Lift - Bernoulli's principle
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Pressure Distribution on Airfoil
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Airfoil Type
Cambered airfoil generated more lift at the same velocity and flow angle than symmetric airfoil
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Airfoil Nomenclature
Suction side
Pressure side
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Lift coefficient .vs. Angle of Attack
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Stall
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Flow Separation
Attached Flow
Separated Flow (Stall)
When stall occurs, an airplane becomes very unstable and hard to control
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Wing Tip Vortex
Flow over 3-D wing
Wingtip vortices are circular patterns of rotating air left behind a wing as it generates lift
Wingtip vortices can pose a hazard to aircraft
Geese in V formation: taking advantage of wing tip vortex
Geese in V formation
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Wingtip vortices are circular patterns of rotating air left behind a wing as it generates lift
Wingtip vortices can pose a hazard to aircraft, especially during the landing and takeoff phases of flight. Air traffic controllers attempt to ensure an adequate separation between departing and arriving aircraft by issuing wake turbulence warnings to pilots.
One theory on migrating bird flight states that many larger bird species fly in a V formation so that all but the leader bird can take advantage of the upwash part of the wingtip vortex of the bird ahead
14
Speed of Sound and Mach Number
Speed of sound (): speed of acoustic waves
Speed of sound is a function of flow property and temperature
Mach number (M): where V is flow velocity and is the speed of sound
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
In dry air at 20 °C (68 °F), the speed of sound is 343.2 meters per second
15
Incompressible Flow
Incompressible flow implies that the density remains constant within a parcel of fluid that moves with the flow velocity.
Incompressible flow assumption holds when Mach number is less than 0.3.
Examples: wind turbine, aircraft during take-off or landing, pipe flow, fan blades, etc.
Equations can be significantly simplified for an incompressible flow and it is easy to solve equations
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Compressible Flow
For high Mach number (>0.3), flows have significant changes in fluid density
Examples: high-speed aircraft, jet engines, rocket motors, hyperloops, high-speed entry into a planetary atmosphere, etc.
Shock waves formed and propagated
Equations are very complicated to solve
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Laminar Flow .vs. Turbulent Flow
Laminar flow: parallel layers
Turbulent flow: irregular fluctuations
Turbulent flow is nature’s most guarded secret.
Reynolds number which is defined as the ratio of inertial forces to viscous forces is used to determine the range of laminar and turbulent flows
High viscous flow
High inertial flow
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Laminar flow (or streamline flow) occurs when a fluid flows in parallel layers, with no disruption between the layers. It is easy to solve.
Turbulent flow is a type of fluid (gas or liquid) flow in which the fluid undergoes irregular fluctuations, or mixing.
Turbulent flow is nature’s most guarded secret. It is extremely difficult to solve, but it happens most of time in reality.
Reynolds number which is defined as the ratio of inertial forces to viscous forces is used to determine the range of laminar and turbulent flows
18
Research Topics – Experimental Aerodynamics
A wind tunnel is a tool used in aerodynamic research to study the effects of air moving past solid objects.
Small scale measurement provides force and momentum that can be extrapolated for a full scale body
Takes a lot of cost and time
NASA Ames Wind Tunnel
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Research Topics – Computational Aerodynamics
Numerical analysis and algorithms are used to solve and analyze problems that involve fluid flows.
Computer simulations takes much less cost and give fast results compared to measurement
Computational fluid dynamics (CFD) is an important research area. The goals are to improve accuracy and speed up simulations
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Research Topics – Hybrid Wind Body
No clear dividing line between the wings and the main body of the craft. Wings are smoothly blended into the body.
Provides efficient high-lift wings and a wide airfoil-shaped body. Offers improved fuel economy and significant noise reduction
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
A Blended wing body (BWB or Hybrid Wing Body, HWB) is a fixed-wing aircraft having no clear dividing line between the wings and the main body of the craft. The form is composed of distinct wing and body structures, though the wings are smoothly blended into the body, unlike a flying wing which has no distinct fuselage. A BWB design may or may not be tailless.
The potential advantages of the BWB approach are efficient high-lift wings and a wide airfoil-shaped body. This enables the entire craft to generate lift, potentially reducing the size and drag of the wings. A blended wing body can have a lift-to-drag ratio significantly greater than a conventional craft, offering improved fuel economy.
21
Research Topics – Rotorcraft Aerodynamics
Lift, propulsion, and control are all provided by rotor blades
Rotor blades experience significant aerodynamic phenomena including shock waves, dynamic stall, blade-vortex interaction, etc.
Rotorcraft aerodynamics is very complicated and difficult to solve
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Research Topics – Wind turbine Aerodynamics
Wind turbines convert flow kinetic energy to rotating machinery energy and eventually useful electricity energy
Aerodynamic lift, drag, thrust, torque are important to understand the wind turbine operation
Turbine wakes make significant impacts on a large wind farm
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Research Topics – Aeroacoustics
Fluid motion generates significant noise due to turbulent flows or body forces (aerodynamically induced noise)
Aircraft noise is a significant issue for government, industry, and public
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
Relevant UC Davis MAE Courses
ENG 103: Fluid Mechanics
EAE 127: Aircraft Aerodynamics
EAE 126: Computational and Theoretical Aerodynamics
Graduate courses: Aeroacoustics, Rotorcraft Aerodynamics, Computational Aerodynamics, etc.
UC Davis, Aeroacoustics Lab
11/21/2016
‹#›
