Basic Aerodynamic Theory Flashcards
(15 cards)
What is the equation of continuity based on ?
Mass flow rate will remain a constant value at all points along the tube. The Equation of Continuity is:
A x V x ρ = Constant . It is based on Law of conservation of mass.
BERNOULLI’S THEOREM
“In the steady flow of an ideal fluid the sum of the pressure and kinetic energy per unit volume remains constant”.
Note: An ideal fluid is both incompressible and has no viscosity. Pressure + Kinetic energy = Constant or:
p + 1/2 ρ V2. Static Pressure + Dynamic Pressure is a constant
What is a Streamline ?
A streamline is the path traced by a particle of air in a steady airflow, and streamlines cannot
cross.
Diverging streamlines illustrate a ______ airflow and resultant __________ pressure and
converging streamlines illustrate an ______ airflow, with resultant _________ pressure.
decelerating, decelerating
decelerating, decreasing
At flow speeds of less than about _______, pressure changes will not affect air density
0.4 M
If the cross sectional area of an airflow is mechanically reduced:
a. The velocity of the airflow remains constant and the kinetic energy increases
b. The velocity of the airflow remains constant and the mass flow increases
c. The mass flow remains constant and the static pressure increases
d. The mass flow remains constant and the velocity of the airflow increases
D
The statement, APressure plus Kinetic energy is constant@, refers to:
a. Bernoulli’s theorem
b. The principle of continuity
c. Newton’s second law of motion
d. The Magnus effect
A
If the velocity of an air mass is increased:
a. The dynamic pressure will decrease and the static pressure will increase
b. The static pressure will remain constant and the kinetic energy will increase
c. The kinetic energy will increase, the dynamic pressure will increase and the static pressure will decrease
d. The mass flow will stay constant, the dynamic pressure will decrease and the static pressure will increase
C
When considering a streamlined airflow, which of the following statements is correct:
1 A resultant decrease in static pressure is indicated by streamlines shown close
together
2 An increase in velocity is indicated by streamlines shown close together
3 Accelerating airflow with a resultant decreasing static pressure is indicated by
converging streamlines
4 Diverging streamlines indicate decelerating airflow with a resultant increasing
static pressure
a. 2 and 4
b. 1, 3 and 4
c. 2, 3 and 4
d. 1, 2, 3 and 4
D
If the pressure on one side of a surface is lower than on the other side:
a. A force per unit area will exist, acting in the direction of the lower pressure
b. No force will be generated, other than drag
c. A force will be generated, acting in the direction of the higher pressure
d. The pressure will leak around the sides of the surface, cancelling-out any pressure
differential
A
When considering a streamtube, which of the following statements is correct:
1 Different sizes of streamtube are manufactured to match the wing span of the aircraft to which they will be fitted
2 A streamtube is a concept to aid understanding of aerodynamic force generation
3 There is no flow into or out of the streamtube through the “walls”, only flow along the tube
4 A streamtube is an imaginary tube made-up of streamlines
a. 1 only
b. 1 and 3
c. 2, 3 and 4
d. 1, 2 and 3
C
At flow speeds less than four tenths the speed of sound, the following will be insignificant:
a. Changes in static pressure due to temperature
b. Changes in density due to static pressure
c. Changes in density due to dynamic pressure
d. Changes in static pressure due to kinetic energy
C
In accordance with the principle of continuity:
1 Air accelerates when the cross-sectional area of a streamline flow is reduced
2 When air accelerates the density of air in a streamline flow is increased
3 Air decelerates when the cross-sectional area of a streamline flow is increased
4 Changes in cross-sectional area of a streamline flow will affect the air velocity
Which of the preceding statements are true:
a. 1, 2, 3 and 4
b. 1 and 4
c. 3 and 4
d. 1, 3 and 4
D
In accordance with Bernoulli’s theorem:
1 If a streamline flow of air decelerates, its kinetic energy will decrease and the
static pressure will increase
2 If a streamline flow of air accelerates, its kinetic energy will increase and the
static pressure will decrease
3 If a streamline flow of air is accelerated, the dynamic pressure will increase and
the static pressure will increase
4 If a streamline flow of air is decelerated, its dynamic pressure will decrease and
the static pressure will increase
the combination of correct statements is:
a. 1, 2, 3 and 4
b. 3 only
c. 1, 2 and 4
d. 3 and 4
C
The statement, “Energy and mass can neither be created nor destroyed, only changed from one form to another”, refers to:
a. Bernoulli’s theorem
b. The equation of kinetic energy
c. The principle of continuity
d. Bernoulli’s principle of continuity
C
