8.2 aerodynamics Flashcards
kinetic energy =
KE = 1/2 p x V2. p = local air density V = is speed in m/s. KE = joules
principle of continuity
energy and mass can neither be created or destroyed. they can only be changed from one form to another
smooth regular airflow patterns around an object are called
laminar flow
turbulent airflow is
when air is disturbed and separates from the surface of a moving body .
a flying body does not attain the speeds necessary to compess air in what region
subsonic region
the speed of airflow is inversely proportional to the area of the cross-section of the tube if the density remains constant.
V1 x A1 = V2 x A2
Principal of continuity
diffuser outlet means
when the diameter increases and the speed decreases
jet outlet means
when the diameter decreases and speed increases
in bernoulis principle using a valve what happens to the pressures
as valve is opened, static press decreases whilst dynamic press increases. the total press is always unchanged.
dynamic pressure =
total pressure - static pressure
dynamic pressure expressed mathematically is
q = 1/2 p x V2
dynamic pressure increases sixteen times if speed increases by how much
4 times
dynamic pressure is indicated to the pilot as
the Indicated Air Speed (IAS)
at the point of stagnation…
the speed of the airflow falls to zero and static press equals total press.if there is no dynamic press, there is no flow
the difference in static pressure acts on the surface to create what force
lift
the boundary layer is
the layer of fluid in the immediate area of a surface
no slip condition is
when air flows over a wing, the fluid at the surface are stationary, as molecules at the surface are brought to rest by friction
after the boundary layer what happens
layers bind to each other but shear slightly relative to the layer beneath them until a layer reaches the velocity of the free stream
the fixed boundary is
where the layer close to the skin of the wing has zero velocity
the moving boundary is
the point where the air has met free air stream velocity
the region between the fixed boundary and moving boundary is called the
boundary layer
if the aircraft velocity is increased what happens to the boundary layer
it becomes thinner
if fluid viscosity is decreased or fluid density is increased what happens to the boundary layer
it becomes thinner
laminar flow is
smooth flow parallel to one another. stream lines not crossing eachother.