Lecture 10 Flashcards
What are the two primary variables related to the operation of a fluid power system?
Pressure and Volume
What happens to the air as you approach sonic speeds?
It becomes a compressible fluid
Speed of Sound
No pressure waves moving in advance of the aircraft
All pressure disturbances are behind the aircraft
Mach number
the speed of the aircraft in relation to the speed of sound
Subsonic
any region below the transonic region or below the critical Mach number
Transonic
begins with first evidence of localized sonic or supersonic airflows and begins at the critical mach number. ends when all flows around aircraft are fuller supersonic
Sonic
right at the speed of sound
Supersonic
any speed faster than the speed of sound
Hypersonic
any speed above mach 5. plasma effects begin to affect airflow
Transonic flow creates the most…
drag on a high speed aircraft
Transonic region
When some flows are supersonic and some are subsonic you are
flying
What happens to drag as you hit Mcrit
Drag rises quickly as the aircraft hits MCRIT, and then
drops of quickly as the aircraft becomes fully supersonic,
and then the drag begins to rise again
Super cruise?
supersonic cruising speed that has the same drag as when the aircraft was still flying subsonic
Normal Shock Wave
Perpendicular to the flow direction
causes tremendous drag
Airflow slows from supersonic to subsonic
Oblique Shock Wave
Inclined to the flow direction
Creates some drag
Airflow slows from high supersonic to low supersonic
These all increase after a shock wave
air pressure, temp, and density
How is lift made if Bernoulli’s Principle no longer applies?`
Lift is generated by the AOA
Sonic Booms
sounds made from pressure waves or shock waves from supersonic objects
What happens to the speed of sound as the air gets colder?
Slows down
What produces large shockwaves?
Large and sudden changes in cross-sectional areas
How to prevent large shockwaves?
Larger overall cross-sectional area, but smaller wing aspect ratio
Smooth transition from wings to fuselage cross section
Whitcomb area rule
a design procedure used to reduce an aircraft’s drag at transonic speeds which occur between Mach .75 and 1.2
Why have wing sweep at subsonic speeds?
yaw stability
Why have wing sweep at high subsonic speeds?
raise the critical mach number
Why have wing sweep at supersonic speeds?
keep wing tips out of shock waves
