ITU Faculty of Aeronautics and Astronautics
Department of Aeronautical Engineering
UCK111E Introduction to Aeronautics and Ethic
2014-2015 Fall Semester Midterm Exam
12.12.2014
Question 1: For incompressible, inviscid, irrotational flow with no body forces the following expression,
which is known as Bernoulli’s equation, holds between any two points of the flow field:
(a) Give the physical meaning of each in term in the equation above.
The pressure coefficient, a dimensionless quantity, is defined as
where the quantities with the
subscript are properties of the freestream region of the flow.
(b) If the freestream velocity is
and at some point in the flow the velocity is , find the pressure
coefficient at this point in terms of the ratio
, i.e.
.
(c) What is the maximum value of the pressure coefficient?
Question 2: Consider an airfoil in a flow at standard sea level conditions with a velocity
point on the airfoil, the pressure is
.
. At a given
(a) Calculate the stagnation pressure.
(b) What is the total pressure?
(c) Calculate the velocity at this point.
Question 3: A U-tube mercury manometer is used to measure the pressure at a point on the wing of a
wind-tunnel model. One side of the manometer is connected to the model, and the other side is open to
the atmosphere. Atmospheric pressure and the density of liquid mercury are
and
. When the displacement of the two columns of mercury is
, with the high column
on the model side, what is the pressure on the wing?
Question 4: A hot air balloon with an inflated diameter of
is carrying a weight of
, which
includes the weight of the hot air inside the balloon. Assuming that the variation of density in the standard
atmosphere is given by
, where is the altitude in meters and is in
, calculate,
(a) the bouyancy force at sea level,
(b) its upward acceleration at sea level at the instant the restraining ropes are released,
(c) the maximum altitude it can achieve.
Question 5: Consider two different flows over geometrically similar airfoil shapes, one airfoil being twice
the size of the other. The flow over the smaller airfoil has freestream properties given by
,
, and
. The flow over the larger airfoil is described by
,
, and
. Assume that both and are proportional to
. Are the flows
dynamically similar?
Question 6: Explain how kites fly. In a figure, show all forces that work on a kite when airborne. Can a kite
fly in still air? If not, why?
Question 7: Define the following: airfoil, camber, thickness, mean camber line, chord line, leading edge,
trailing edge, angle of attack, sweep angle, planform area. Also draw a figure representing these airfoil and
wing characteristics.
Question 8: An aircraft is flying at a velocity
. The angle of attack of the wing is
(a) At some instant the aircraft experiences a gust of
of attack at this instant.
(b) At some other instant the gust wind makes an angle of
of attack.
.
in upward direction. Calculate the angle
with the horizontal. Find the new angle
Question 9: How is an aircraft stabilized about its vertical, lateral and longitudinal axes? Show this in a
figure.
Question 10: Define the critical mach number.
Question 11: Will the aspect ratio be the same for two geometrically similar wings? What can you say
about the planform areas?
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