Podcast
Questions and Answers
What is the primary cause of form drag?
What is the primary cause of form drag?
- Frictional shear stress integrated over the surface
- Mutual interaction of flow fields around each component
- Lift generation
- Separated air flow (correct)
If the indicated air speed is tripled, what will be the effect on parasite drag?
If the indicated air speed is tripled, what will be the effect on parasite drag?
- It will be increased by a factor of nine (correct)
- It will remain the same
- It will be reduced by half
- It will be reduced to one ninth of its original value
What type of drag is associated with the generation of lift?
What type of drag is associated with the generation of lift?
- Zero-lift drag
- Induced drag (correct)
- Parasite drag
- Wave drag
What is the sum of skin friction drag and form drag?
What is the sum of skin friction drag and form drag?
What type of drag exists when the airplane is at zero lift angle of attack?
What type of drag exists when the airplane is at zero lift angle of attack?
What is the primary factor that affects the frontal area presented to the airflow?
What is the primary factor that affects the frontal area presented to the airflow?
What is the primary reason for the decrease in induced drag with an increase in aircraft speed?
What is the primary reason for the decrease in induced drag with an increase in aircraft speed?
Why does induced drag decrease with an increase in aspect ratio for a given lift force?
Why does induced drag decrease with an increase in aspect ratio for a given lift force?
What is the primary purpose of wing end plates in reducing induced drag?
What is the primary purpose of wing end plates in reducing induced drag?
What is the effect of tip tanks on the wing bending moment?
What is the effect of tip tanks on the wing bending moment?
What is the primary reason for the increase in parasite drag coefficient due to airframe contamination?
What is the primary reason for the increase in parasite drag coefficient due to airframe contamination?
What is the direction of air movement around the airfoil tips?
What is the direction of air movement around the airfoil tips?
What is the relationship between lift and weight in certain maneuvers?
What is the relationship between lift and weight in certain maneuvers?
What is the effect of airfoil's tips vortex on the wing's performance?
What is the effect of airfoil's tips vortex on the wing's performance?
What is the effect of increasing weight on induced drag?
What is the effect of increasing weight on induced drag?
What is the relationship between the Indicated Air Speed (IAS) and the Angle of Attack (𝛼) with respect to induced drag?
What is the relationship between the Indicated Air Speed (IAS) and the Angle of Attack (𝛼) with respect to induced drag?
What is the primary purpose of employing de-icing and anti-icing devices on airframes?
What is the primary purpose of employing de-icing and anti-icing devices on airframes?
What is the term used to describe the whirlpool of air formed at the airfoil tips?
What is the term used to describe the whirlpool of air formed at the airfoil tips?
What happens to the flow if the turbulence intensity is large enough?
What happens to the flow if the turbulence intensity is large enough?
What can alter the effective Reynolds number in turbulent flow?
What can alter the effective Reynolds number in turbulent flow?
What is the primary research tool for studying turbulent air/gas flow?
What is the primary research tool for studying turbulent air/gas flow?
What happens to the flow angularity in high turbulence levels?
What happens to the flow angularity in high turbulence levels?
Why can wind tunnels with identical levels of turbulence produce different test results?
Why can wind tunnels with identical levels of turbulence produce different test results?
What can turbulence excite in turbulent flow?
What can turbulence excite in turbulent flow?
What is the primary reason for maintaining a long contraction length in a wind tunnel?
What is the primary reason for maintaining a long contraction length in a wind tunnel?
What is the consequence of flow separation in the contraction region?
What is the consequence of flow separation in the contraction region?
What is the effect of a finite-length inlet contraction on the wall static pressure distribution?
What is the effect of a finite-length inlet contraction on the wall static pressure distribution?
What is the primary factor that dictates the final turbulence intensity levels in the test section?
What is the primary factor that dictates the final turbulence intensity levels in the test section?
What is the desired flow characteristic at the exit of the contraction?
What is the desired flow characteristic at the exit of the contraction?
Study Notes
- Airframe contamination by ice, frost, snow, mud, or slush increases parasite drag coefficient, and severe airframe icing affects the airframe's area.
- De-icing and anti-icing devices are employed on prone areas to reduce parasite drag.
- Induced drag is caused by wing tip vortices, which occur when an airfoil is flown at a positive angle of attack, resulting in a pressure differential between the upper and lower surfaces.
- The pressure difference causes air to move from the bottom of the airfoil outward from the fuselage around the tips, creating a whirlpool of air called a vortex.
- The wing must be flown at a higher angle of attack to replace the lost lift, increasing drag, and lower indicated air speeds result in stronger vortices and greater induced drag.
- Flaps are devices used to increase lift during takeoff and landing, and different types include plain, split, slotted, Fowler, slotted Fowler, Gouge, Junkers, Zap, and Krueger flaps.
- Types of drag include skin friction drag, form drag, profile drag, interference drag, parasite drag, induced drag, and wave drag.
- Parasite drag varies with the square of the indicated air speed and is affected by the frontal area presented to the airflow.
- Factors affecting induced drag include the size of lift, aircraft speed, aspect ratio, and weight, and induced drag decreases with increasing speed and aspect ratio.
- Wing end plates and tip tanks can reduce induced drag, as they restrict tip vortices and reduce the wing bending moment.
- Turbulence in wind tunnel tests can produce incorrect measurements of drag, lift, and velocity profiles, and can alter the behavior of the boundary layer and skin friction.
- Hot-Wire Anemometry is a chief research tool for measuring turbulent air/gas flow parameters such as turbulent intensity, mean velocity, and root mean squares.
- The contraction of the wind tunnel should be kept long to minimize boundary layer growth and reduce the effect of Gortler vortices, ensuring uniform and steady flow into the test section.
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Description
Learn about the different types of flaps used in aircraft, including plain, split, slotted, and Fowler flaps. Understand the history and purpose of flaps, and how they affect drag measurements.
