MIDTERM

Question 1

When a fluid is in motion, it must move in such a way that mass is conserved.

Answer 1

CONTINUITY EQUATION

Question 2

can neither be created
nor destroyed.

Answer 2

Mass

Question 3

As long as the flow is steady, the mass that flows through the cross-section at point 1 must be the same as the mass
that flows through the cross section at point 2

Answer 3

CONTINUITY EQUATION

Question 4

As long as the flow is steady, the mass that flows through the cross-section at point 1 must be _______ as the mass that flows through the cross section at point 2

Answer 4

the same

Question 5

Since the mass at point 1 is the same at point 2.

Answer 5

CONTINUITY EQUATION

Question 6

Sound waves travel through the air at a definite speed

Answer 6

speed of sound

Question 7

This is obvious from natural observation; a lightning bolt is observed in the distance, and the thunder is heard some time later

Answer 7

SPEED OF SOUND

Question 8

The _______________ in a perfect gas depends only on the temperature of the
gas.

Answer 8

speed of sound

Question 9

is a function of the
temperature.

Answer 9

Speed of sound

Question 10

is the flow velocity
divided by the speed of sound.

Answer 10

MACH NUMBER

Question 11

Named after Ernst Mach

Answer 11

MACH NUMBER

Question 12

As the speed of the object approaches the speed of sound, the flight __________ is nearly equal to 1, and the flow
is said to be transonic.

Answer 12

mach number

Question 13

0-0.8

Answer 13

Subsonic

Question 14

0.81-1.2

Answer 14

Transonic

Question 15

1

Answer 15

Sonic

Question 16

1.21-5.0

Answer 16

Supersonic

Question 17

5.1-25.0

Answer 17

Hypersonic

Question 18

> 25.1

Answer 18

Ultrasonic

Question 19

are large tubes with air
moving inside.

Answer 19

Wind tunnels

Question 20

The ________ are used to copy the actions of an object in flight.

Answer 20

tunnels

Question 21

Researchers use _______ to learn more about how an aircraft will fly.

Answer 21

wind tunnels

Question 22

is a device for testing aircraft and its components in a controlled airstream under laboratory conditions.

Answer 22

WIND TUNNELS

Question 23

Most of the time, powerful fans move air through the tube. The object to be tested is fastened in the tunnel so that it will not move.

Answer 23

WIND TUNNELS

Question 24

____________ can be placed in the air to observe
the movement of air.

Answer 24

Smoke or dye

Question 25

_________ and _______ put a model of an airplane in the tunnel and then study the way air moves around the model.

Answer 25

Scientists and Engineers

Question 26

The models are usually made out of steel or aluminum, that are tested and loaded with many instruments and sensors that report back to the computers in the control room.

Answer 26

WIND TUNNELS

Question 27

___________ use wind tunnels to test models of proposed aircraft.

Answer 27

Aerodynamicists

Question 28

In the _______, the engineer can carefully control the flow conditions which affect forces on the aircraft.

Answer 28

tunnel

Question 29

By the use of wind tunnels, we are able to explore the lift, drag, side force, pitching, rolling, and yawing moment of an aircraft.

Answer 29

FORCES

Question 30

_________ are designed for a specific purpose and speed range.

Answer 30

Wind tunnels

Question 31

different types of wind tunnels

Answer 31

- Low-Speed Wind Tunnels - Transonic Wind Tunnels - Supersonic Wind Tunnels - Hypersonic Wind Tunnels

Question 32

are used form operations at very low Mach Number, with speeds in the test section up to 400 km/h (M=0.3)

Answer 32

Low-speed wind tunnels

Question 33

These types of Wind tunnels are able to achieve speeds close to the speed of sound. The highest speed is reached in the test section.

Answer 33

Transonic Wind Tunnels

Question 34

should produce supersonic speeds (Mach numbers up to 5)

Answer 34

Supersonic wind tunnels

Question 35

achieved with an appropriate design of a convergent-divergent nozzle. When the sonic speed is reached in throat, the flow accelerates in a nozzle supersonically

Answer 35

Supersonic Wind Tunnels

Question 36

is designed to generate a hypersonic flow field in the working section.

Answer 36

hypersonic wind tunnel

Question 37

As with supersonic wind tunnels, these types of tunnels must run intermittently with very high-pressure ratios when initializing.

Answer 37

hypersonic wind tunnel

Question 38

In subsonic wind tunnels, a convenient way of measuring the pressure difference (P1-P2)

Answer 38

MANOMETER

Question 39

is a measure of the purely random motion of molecules in the gas.

Answer 39

STATIC PRESSURE

Question 40

is due simply to the random motion of the molecules.

Answer 40

STATIC PRESSURE

Question 41

can also be the pressure of the air around the aircraft at a certain point.

Answer 41

STATIC PRESSURE

Question 42

is related to the velocity of the air. It represents the kinetic energy per unit volume of a fluid due to its motion.

Answer 42

DYNAMIC PRESSURE

Question 43

is the measure of the impact pressure or “ram air” pressure caused by the forward motion of the aircraft through the air.

Answer 43

DYNAMIC PRESSURE

Question 44

is the sum of the free-stream dynamic pressure and free-stream static pressure.

Answer 44

TOTAL PRESSURE

Question 45

At a stagnation point, the fluid velocity is ____.

Answer 45

zero

Question 46

In the case where the fluid is ______, Total Pressure is also the same as the static pressure.

Answer 46

not moving

Question 47

The pitot tube was invented by a Frenchman,

Answer 47

Henri Pitot

Question 48

It is an instrument that measures the total pressure at a point in the flow.

Answer 48

PITOT TUBE

Question 49

The ___________ is obtained through a static port.

Answer 49

static pressure

Question 50

The ___________ is most often a flush-mounted hole on the fuselage of an aircraft.

Answer 50

static port

Question 51

A ___________ is a system of pressure-sensitive instruments that is most often used in aviation.

Answer 51

Pitot-Static system

Question 52

It consists of a pitot tube, a static port, and the pitot-static instruments.

Answer 52

PITOT-STATIC SYSTEM

Question 53

The speed of these tunnels varies from Mach 5 to 15.

Answer 53

Hypersonic wind tunnels

Question 54

________ travel through the air at a definite speed

Answer 54

Sound waves