Technology & Engineering
Lift Force
Lift force is the aerodynamic force that enables an aircraft to overcome gravity and stay airborne. It is generated by the interaction between the aircraft's wings and the air, creating a pressure difference that results in an upward force. Lift force is essential for flight and is a fundamental concept in aerodynamics and aircraft design.
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6 Key excerpts on "Lift Force"
- Jonathan Wickert, Jonathan Wickert, Kemper Lewis(Authors)
- 2016(Publication Date)
- Cengage Learning EMEA(Publisher)
Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 6.7 Lift Force 257 ▸ ▸ 6.7 Lift Force S imilar to drag, the Lift Force is also produced by the relative motion between a solid object and a fluid. While the drag force acts in parallel to the direction of the fluid’s flow, the Lift Force acts in perpendicular to it. For instance, in the context of the airplane shown in Figure 6.27, the high-speed flow of air around the wings generates a vertical Lift Force F L that balances the plane’s weight. Four forces are shown acting on the aircraft in flight: the plane’s weight w , the thrust F T produced by its jet engines, the lift F L produced by the wings, and the drag F D that opposes the motion of the plane through the air. In steady level flight, those forces balance to keep the plane in equilibrium: the engines’ output overcomes wind resistance, and the wings’ lift supports the weight of the aircraft. Lift Force is important not only for aircraft wings and other flight control surfaces, but also for the design of propeller, compressor, and turbine blades; ship hydrofoils; and the body contours of commercial and racing automobiles. The area of mechanical engineering that encompasses the interaction between structures and the air flowing around them is called aerodynamics . When engineers are performing aerodynamic analysis of drag and Lift Forces, invariably they make approximating assumptions with respect to geometry and the behavior of the fluid. For instance, neglecting a fluid’s viscosity or compressibility Aerodynamics Example 6.9 | continued Because this is less than one, we have confirmed that it was acceptable to apply Equation (6.16). Had we found otherwise, we would have discarded this prediction, and instead applied Equation (6.14) with the graph of Figure 6.23 for C D .
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter 2 Lift (force) and Drag Lift (force) Airbus A380 taking off during the Paris Air Show in 2007. A fluid flowing past the surface of a body exerts a surface force on it. Lift is defined to be the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is defined to be the component of the surface force parallel to the flow direction. ____________________ WORLD TECHNOLOGIES ____________________ Overview Forces on an airfoil. If the fluid is air, the force is called an aerodynamic force. An airfoil is a streamlined shape that is capable of generating significantly more lift than drag. Aerodynamic lift is commonly associated with the wing of a fixed-wing aircraft, although lift is also generated by propellers; kites; helicopter rotors; rudders, sails and keels on sailboats; hydrofoils; wings on auto racing cars; wind turbines and other streamlined objects. While common meanings of the word lift suggest that lift opposes gravity, lift can be in any direction. When an aircraft is flying straight and level (cruise) most of the lift opposes gravity. However, when an aircraft is climbing, descending, or banking in a turn, for example, the lift is tilted with respect to the vertical. Lift may also be entirely downwards in some aerobatic manoeuvres, or on the wing on a racing car. In this last case, the term downforce is often used. Lift may also be horizontal, for instance on a sail on a sailboat. Non-streamlined objects such as bluff bodies and plates (not parallel to the flow) may also generate lift when moving relative to the fluid. This lift may be steady, or it may oscillate due to vortex shedding. Interaction of the object's flexibility with the vortex shedding may enhance the effects of fluctuating lift and cause vortex-induced vibrations. Description of lift on an airfoil There are several ways to explain how an airfoil generates lift.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter 6 Lift (force) and Drag Lift (force) Airbus A380 taking off during the Paris Air Show in 2007. A fluid flowing past the surface of a body exerts a surface force on it. Lift is defined to be the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is defined to be the component of the surface force parallel to the flow direction. ____________________ WORLD TECHNOLOGIES ____________________ Overview Forces on an airfoil. If the fluid is air, the force is called an aerodynamic force. An airfoil is a streamlined shape that is capable of generating significantly more lift than drag. Aerodynamic lift is commonly associated with the wing of a fixed-wing aircraft, although lift is also generated by propellers; kites; helicopter rotors; rudders, sails and keels on sailboats; hydrofoils; wings on auto racing cars; wind turbines and other streamlined objects. While common meanings of the word lift suggest that lift opposes gravity, lift can be in any direction. When an aircraft is flying straight and level (cruise) most of the lift opposes gravity. However, when an aircraft is climbing, descending, or banking in a turn, for example, the lift is tilted with respect to the vertical. Lift may also be entirely downwards in some aerobatic manoeuvres, or on the wing on a racing car. In this last case, the term downforce is often used. Lift may also be horizontal, for instance on a sail on a sailboat. Non-streamlined objects such as bluff bodies and plates (not parallel to the flow) may also generate lift when moving relative to the fluid. This lift may be steady, or it may oscillate due to vortex shedding. Interaction of the object's flexibility with the vortex shedding may enhance the effects of fluctuating lift and cause vortex-induced vibrations. Description of lift on an airfoil There are several ways to explain how an airfoil generates lift.
- Jonathan Wickert, Kemper Lewis, Jonathan Wickert(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 6.7 Lift Force 257 ▸ ▸ 6.7 Lift Force S imilar to drag, the Lift Force is also produced by the relative motion between a solid object and a fluid. While the drag force acts in parallel to the direction of the fluid’s flow, the Lift Force acts in perpendicular to it. For instance, in the context of the airplane shown in Figure 6.27, the high- speed flow of air around the wings generates a vertical Lift Force F L that balances the plane’s weight. Four forces are shown acting on the aircraft in flight: the plane’s weight w, the thrust F T produced by its jet engines, the lift F L produced by the wings, and the drag F D that opposes the motion of the plane through the air. In steady level flight, those forces balance to keep the plane in equilibrium: the engines’ output overcomes wind resistance, and the wings’ lift supports the weight of the aircraft. Lift Force is important not only for aircraft wings and other flight control surfaces, but also for the design of propeller, compressor, and turbine blades; ship hydrofoils; and the body contours of commercial and racing automobiles. The area of mechanical engineering that encompasses the interaction between structures and the air flowing around them is called aerodynamics. When engineers are performing aerodynamic analysis of drag and Lift Forces, invariably they make approximating assumptions with respect to geometry and the behavior of the fluid. For instance, neglecting a fluid’s viscosity or compressibility Aerodynamics Example 6.9 | continued Because this is less than one, we have confirmed that it was acceptable to apply Equation (6.16). Had we found otherwise, we would have discarded this prediction, and instead applied Equation (6.14) with the graph of Figure 6.23 for C D .
eBook - ePubFlight Theory and Aerodynamics
A Practical Guide for Operational Safety
- Joseph R. Badick, Brian A. Johnson(Authors)
- 2021(Publication Date)
- Wiley-Interscience(Publisher)
4 LiftCHAPTER OBJECTIVES
After completing this chapter, you should be able to:- Summarize the importance of angle of attack in the production of lift, and identify how angle of attack indicators improve safety of flight.
- Describe boundary layer theory, contrast laminar and turbulent flow, and characterize how Reynolds number is used to measure different flow regimes.
- Define adverse pressure gradient and illustrate how it relates to airflow separation.
- Correlate angle attack and the development of an airplane stall, identifying conditions of flight when stalls occur.
- Identify the factors involved in the development of aerodynamic force equations.
- Describe the variables within the lift equation, explain how each variable affects the production of lift, and reconstruct the lift equation to solve for each variable.
- Analyze airfoil lift characteristics as camber and thickness are varied.
- Provide examples of high coefficient of lift devices and how each device influences the production of lift.
INTRODUCTION TO LIFT
Lift is most commonly associated with the wings of a fixed‐wing aircraft, although lift is also generated by propellers, helicopter rotors, rudders, sails and keels on sailboats, hydrofoils, wings on auto racing cars, and wind turbines.While the common meaning of the word “lift” assumes that lift opposes weight, lift in the technical sense, used in this discussion, can be in any direction with respect to gravity, since it is defined with respect to the direction of flow, rather than to the direction of gravity.When an aircraft is flying straight and level, as in cruise flight, most of the lift opposes weight, which is always directed vertically downward, regardless of the attitude of the aircraft. However, when an aircraft is climbing, descending, or maneuvering in a turn, the lift vector is tilted at an angle with respect to the vertical. Lift may also be entirely downward in some aerobatic maneuvers. In this last case, the term downforce is often used. Lift may also be largely horizontal, for instance on a sail for a sailboat.
No longer available |Learn moreThe Pilot's Manual: Ground School
Pass the FAA Knowledge Exam and operate as a private or commercial pilot
- (Author)
- 2022(Publication Date)
- Aviation Supplies & Academics, Inc.(Publisher)
Aerodynamics 1 Forces Acting on an Airplane 2 Stability and Control 3 Aerodynamics of Flight 3 Chapter 1 Forces Acting on an Airplane Like all things, an airplane has weight, the force of gravity that acts through the center of the airplane in a vertical direction toward the center of the earth. While the airplane is on the ground, its weight is supported by the force of the ground on the airplane, which acts upward through the wheels. During the takeoff roll, the task of supporting the weight of the airplane is transferred from the ground to the wings (and vice versa during the landing). While in level flight, the weight of the airplane is supported by the Lift Force, which is generated aerodynamically by the flow of air around the wings. In addition, as the airplane moves through the air it will experience a retarding force known as drag, which, unless counteracted, will cause the airplane to decelerate and lose speed. In steady (unaccelerated) straight-and-level flight, the drag (or retarding force) is neutralized by the thrust (figure 1-2). In most smaller airplanes, thrust is produced by the engine–propeller combination; in pure-jet airplanes, the thrust is produced by the gas efflux, without the need for a propeller. In figure 1-3, the forces are equal and opposite, canceling each other out, so that the resultant force acting on the airplane is zero, and it will neither accel- erate nor decelerate. In this situation the airplane is in a state of equilibrium: • weight is equal to lift, and acts in the opposite direction; and • drag is equal to thrust, and acts in the opposite direction. During steady (unaccelerated) flight the four main forces are in equilibrium and the airplane will continue in level flight at the same speed. For the type of airplane you are likely to be flying during your training, the amount of the lift (and therefore the weight) during cruise flight will be approximately 10 times greater than the drag (and thrust).
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