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aerodynamics > aero midterm > Flashcards

aero midterm Flashcards

1
Q

Temperature is a measure of the average ______ energy of the particles in a gas

A

kinetic

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2
Q

A perfect gas is one in which intermolecular forces are negligible.

A

True

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3
Q

the equation of state for a perfect gas is given by…

A

p = rhoRT

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4
Q

What are the sources of aerodynamic forces acting on a body

A

pressure distribution and shear stress distribution over the surface

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5
Q

In isothermal regions of the standard atmosphere, temperature s said to change as altitude changes

A

False

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6
Q

in both the gradient and isothermal regions of the standard atmosphere, the pressure ____ with an increase in altitude

A

decreases

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7
Q

The continuity equation for steady fluid flow states that

A

rho1A1V1 = rho2A2V2

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8
Q

For incompressible flow

A

rho1 = rho2

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9
Q

You are given a convergent duct for which the inlet area A1 is greater than the outlet area A3. Assuming that flow in this duct is incompressible, the velocity of the flow will _____ as it moves through the duct.

A

increase

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10
Q

An inviscid flow is one that is frictionless

A

true

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11
Q

An isentropic process is one that is both adiabatic and reversible. Thus, an isentropic process is one in which there is _____ .

A

neither heat exchange nor any effects due to friction

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12
Q

the speed of sound in a perfect gas depends only on the temperature of the gas.

A

true

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13
Q

Mach number is the ratio of the flow velocity to the speed of sound. If a flow has M = 1, the flow is said to be ____ .

A

sonic

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14
Q

Consider a subsonic wind tunnel with a typical upstream-to-downstream arrangement consisting of a reservoir, nozzle, test section, and diffuser. In such a wind tunnel, the test section pressure is ______ than the reservoir pressure.

A

smaller than

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15
Q

In a subsonic wind tunnel, a manometer is used to measure the _____ difference between the nozzle and test section.

A

pressure

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16
Q

The ____ at a given point in a flow is the pressure that would exist if the flow were slowed down isentropically to zero velocity.

A

total pressure

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17
Q

A pressure gauge connected to a pitot static probe measures the difference between the ____.

A

total and static pressure

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18
Q

Flow speeds below M = 0.3 are

A

incompressible

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19
Q

Flow speeds above M = 0.3 are

A

compressible

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20
Q

shock waves are very thin regions of the flow across which some severe changes in the flow properties take place. Assuming that the perfect gas assumption exists, as a fluid element flows through a shock wave, the total temperature T0 _____.

A

stays the same

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21
Q

Consider an airplane flying at some true airspeed at some altitude. It’s equivalent airspeed at this condition is defined as the velocity at which it would have to fly at standard sea level to experience the dame dynamic pressure.

A

True

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22
Q

The area velocity relation states that, for supersonic flows (M>1), the cross sectional area must _____ for the velocity to increase.

A

increase

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23
Q

Flow speeds below Mach 0.3 are typically treated as incompressible because the ____ is essentially constant at these speeds.

A

density

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24
Q

flow that consits of friction is known as _____ flow

A

viscous

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25
Q

flow that consists of friction is known as _____ flow

A

viscous

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26
Q

The flow in a boundary layer consists of a velocity profile which exhibits a change in flow velocity between the object’s surface and the outer edge of the boundary layer. Let the velocity at the surface be given by V1 and the velocity at the outer edge of the boundary layer be given by V2. Which of the following describes the velocity profile in the boundary layer?

A

V1 < V2

27
Q

Consider viscous flow over a flat plate. As the air flows across the surface from the leading edge to the trailing edge (ie. front to back), one would expect the thickness of the boundary layer to _______.

A

increase

28
Q

Laminar flow is one in which the streamlines break up and a fluid element moves in a random, irregular, and tortuous fashion.

A

False

29
Q

Consider viscous flow over a surface. The flow in the boundary layer may be categorized as laminar or turbulent. The presence of fiction creates a shear stress at the surface tau-w . Let tau-w-laminar represent this shear stress in the case of laminar flow and tau-w-turbulent represent this shear stress in the case of turbulent flow. Which of the following is accurate?

A

tau-w-laminar < tau-w-turbulent

30
Q

Under the same flow conditions, a turbulent boundary layer will be thicker than a laminar boundary layer.

A

True

31
Q

Consider a flat plate boundary layer in a compressible flow. In such a case, for a constant Reynolds number, the effect of increasing the freestream Mach number M_inf is to _______ the local skin friction coefficient c_f_x.

A

decrease

32
Q

The major consequences of flow separation over an airfoil are _______ .

A

a large decrease in lift and a large increase in drag

33
Q

In the presence of an adverse pressure gradient, fluid elements along a streamline within the boundary layer tend to _______ .

A

slow down

34
Q

Skin friction drag is caused by flow separation at the surface of the object.

A

False

35
Q

Pressure drag due to separation can be reduced by establishing a turbulent boundary layer on the surface.

A

True

36
Q

The lift of an airfoil L is always defined as the component of the aerodynamic force _______ to the _______.

A

perpendicular/ relative wind

37
Q

The normal and axial forces of an airfoil may be related to the lift and drag of the airfoil through the angle of attack.

A

True

38
Q

The moment coefficient c_m is obtained by dividing the moment M by which of the following?

A

q_infSc

39
Q

The lift slope is given by the slope of the linear portion of a plot of:

A

cl vs alpha

40
Q

A positively cambered airfoil will have a non-zero value of cl at zero angle of attack.

A

true

41
Q

At some angle of attack larger than that corresponding to cl_max , the flow around an airfoil typically remains attached.

A

False

42
Q

At high subsonic Mach numbers in a flow, the associated compressibility effects have no influence on the low-speed pressure coefficient.

A

False

43
Q

Consider a flat plate at a positive angle of attack in a flow field with freestream velocity of M_inf > 1. At the leading edge on the upper surface of this flat plate, one would observe a/an _______ .

A

expansion wave

44
Q

At subsonic speeds below the drag-divergence Mach number, one would expect to have a significant amount of wave drag.

A

false

45
Q

For values of Mach number between M = M_dragdivergence and M = 1 , one would expect _______ in the drag coefficient cd.

A

an increase

46
Q

The only two sources of Aerodynamic forces on a body are

A

Pressure and Shear Stress

47
Q

Total Pressure is the pressure you would feel if you were traveling along with a fluid element in a flow

A

False

48
Q

Static Pressure is the pressure you would feel if you were traveling along with a fluid element in a flow

A

True

49
Q

Compressible flows that are isentropic (adiabatic and reversible) have constant static temperatures throughout the flow since both heat addition and friction are ignored

A

False

50
Q

As altitude increases in the troposphere below the tropopause, the speed of sound

A

decreases

51
Q

At sea level, the true and equivalent velocities are equal

A

True

52
Q

Assuming compressible, steady, isentropic flow, and a constant mass flow rate, if the flow entering a duct is supersonic, to decrease its velocity, you must ____ the area along the direction of the flow.

A

decrease

53
Q

when you have achieved choked flow in the throat of a nozzle you can continue to increase the mass flow rate by continuing to decrease the pressure at the exit of the nozzle.

A

False

54
Q

The equation of state for an ideal gas states the relationship between pressure, temperature, and density of an ideal gas at different points in the same flow

A

false

55
Q

The assumptions used to derive both Bernoulli’s Equation and the energy equation result in both total pressure and total temperature being constant along a streamline.

A

True

56
Q

Aerodynamics is defined as the science that deals with the transfer of energy

A

False

57
Q

Pressure is a scalar quantity and can be defined in cartesian space by one component

A

True

58
Q

velocity is just another word for speed; there is no technical difference between them.

A

False

59
Q

The static pressure at a given point is the pressure we would feel if the flow were brought isentropically to rest at that point.

A

False

60
Q

The conservation of momentum is another form of Newton’s Second Law of motion

A

True

61
Q

The velocity always increases in a convergent nozzle

A

False

62
Q

Because there is no heat transfer in an isentropic process, the temperature of the flow must remain constant everywhere in the flow.

A

False

63
Q

The total pressure and total temperature remain constant across a shock wave.

A

False (total pressure decreases)

aerodynamics (1 decks)

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