Shock Waves

Question 1

What is Mach number ?

Answer 1

It is the ratio of the speed of object to the speed of sound in the same medium

Question 2

What is an acoustic wave ?

Answer 2

It is simply a sound wave

Question 3

What is the velocity of a sound wave at STP in air ?

Answer 3

Around 333 m/s

Question 4

What are the frequencies acoustic waves lie in ?

Answer 4

20 to 20,000 Hz

Question 5

What are ultrasonic waves ?

Answer 5

Pressure waves that have frequencies greater than 20,000 Hz

Question 6

What is the speed of an ultrasonic wave ?

Answer 6

Same speed as sound

Question 7

What is a subsonic wave ?

Answer 7

A mechanical waves moving in a fluid with velocity less than that of sound

Question 8

What is the Mach number so subsonic waves ?

Answer 8

Less than 1

Question 9

What are some examples of subsonic motion ?

Answer 9

Vehicles such as motor cars and trains, birds

Question 10

Where does the sound emitted by a body moving with subsonic motion go ?

Answer 10

It goes ahead of the body and moves away

Question 11

What is a supersonic wave ?

Answer 11

It is a mechanical wave which travels with a speed greater than that of sound

Question 12

Where does the sound emitted by a body travelling with supersonic speed go ?

Answer 12

The body moves ahead by piercing it’s own sound curtain

Question 13

What kind of wave is formed by supersonic motion ?

Answer 13

A series of expanding sound waves, with their centers continuously displaced along trajectory

Question 14

What is the amplitude of a supersonic wave ?

Answer 14

It is high, and affects the medium

Question 15

What is Mach cone, formed at supersonic speed ?

Answer 15

A number of tangents drawn to the expanding sound waves for a Mach cone

Question 16

What are hypersonic waves ?

Answer 16

Mach number greater than 5 Special case of supersonic waves

Question 17

What are transonic waves ?

Answer 17

Mach number in between 0.8 and 1.2 Domain in which change of phase from subsonic to supersonic occurs

Question 18

What is a shock wave ?

Answer 18

It is a surface that manifests as a sudden discontinuity in a fluid medium, in which it is propagating with supersonic speed

Question 19

What does a shock wave cause ?

Answer 19

Sudden increase in pressure, temperature and density of gas through which it propagates

Question 20

What is a closed system ?

Answer 20

A system that does not exchange matter with outside and not acted upon by external forces

Question 21

What is the law of conservation of matter ?

Answer 21

The total mass of any isolated system remains unchanged, regardless of any physical or chemical change within it

Question 22

What is the law of conservation of momentum ?

Answer 22

In a closed system, total momentum remains constant

Question 23

What is the law of conservation of energy ?

Answer 23

The total energy of a closed system remains constant and is independent of any changes within the system

Question 24

What is extra-corporal lithitripsy ?

Answer 24

It is a shock wave therapy for treating kidney stones

Question 25

What happens in it ?

Answer 25

The kidney stones are shattered into fragments

Question 26

What happens to the shattered kidney stones ?

Answer 26

Smoothly passed out through urinary tracts

Question 27

How can shock waves assist in drug delivery ?

Answer 27

It can replace needles

Question 28

How are drugs delivered using shock waves ?

Answer 28

The drug is kept in a cartridge and pressed to the skin

Question 29

How does the shock wave enter ?

Answer 29

Directly through the porosity of the skin

Question 30

What is the normal penetration ?

Answer 30

About 100 microns

Question 31

Is it painless ?

Answer 31

Yes

Question 32

How is wood softened in pencil industries ?

Answer 32

By soaking in a polymer

Question 33

At what temperature ?

Answer 33

70 C

Question 34

For how long ?

Answer 34

About three hours

Question 35

How long does it take for the wood to dry ?

Answer 35

Days

Question 36

How do shock waves assist the pencil industry ?

Answer 36

Shock waves are sent through the liquid itself

Question 37

What happens to the wood ?

Answer 37

The liquid immediately enters the wood

Question 38

What happens to the drying time ?

Answer 38

Reduces drastically

Question 39

Can a shock wave be used to push DNA into a cell ?

Answer 39

Yes

Question 40

What is the distinguishing feature of this ?

Answer 40

The functionality of DNA is unaffected by impact of the shock wave

Question 41

How do shock waves assist in study of gas dynamics ?

Answer 41

Extreme conditions of pressure and temperature that are produced in shock tube, allows us to study high temperature gas dynamics

Question 42

How does water enter borewells ?

Answer 42

Water from feeder sources accumulates in borewell through a number of porous seepage points

Question 43

How do shock waves assist in treatment of dry borewells ?

Answer 43

Clears blockages of seepage routes by sand particles

Question 44

What principle does the Reddy Tube operate on ?

Answer 44

FPST

Question 46

What is the full form of FPST

Answer 46

Free Piston driven shock tube

Question 48

How is Reddy tube operated ?

Answer 48

By hand

Question 50

What is the Mach number of waves produced by Reddy shock tube ?

Answer 50

Above 1.5

Question 52

How is the rupture pressure determined ?

Answer 52

It is a function of the thickness of diaphragm

Question 54

What is the shape of Reddy tube ?

Answer 54

Cylindrical

Question 56

What is it made up of ?

Answer 56

Stainless Steel

Question 58

What is the diameter ?

Answer 58

30 mm

Question 60

What is its length ?

Answer 60

1 m

Question 62

What are the names of those sections separated by a diaphragm ?

Answer 62

Driver tube and Driven tube

Question 64

What is the thickness of the diaphragm ?

Answer 64

0.1 mm

Question 66

What is it made up of ?

Answer 66

Aluminium, Mylar or Paper

Question 68

Where is the piston fitted ?

Answer 68

Far end of the driver section

Question 70

What is there at the end of the driven section or downstream end ?

Answer 70

It is closed

Question 72

Where is the digital pressure gauge mounted ?

Answer 72

Next to the diaphragm in the driver section

Question 74

How is the driver gas compressed ?

Answer 74

By the action of the piston

Question 75

What happens following the rupturing of the diaphragm ?

Answer 75

The driver gas rushes and pushes driven gas to downstream end, generating a moving shock wave

Question 76

What happens to the primary shock wave ?

Answer 76

It is reflected at the downstream end

Question 77

What happens to the test gas after reflection ?

Answer 77

It goes through further compression, boosting T&P

Question 78

How is the compression reduced with time ?

Answer 78

The expansion wave reflected from the upstream end arrives and neutralises it

Question 79

When is the expansion wave created ?

Answer 79

The moment the diaphragm ruptures

Question 80

In which direction does the expansion wave move ?

Answer 80

Opposite to the shock wave

Question 81

How long is the high T&P sustained at the downstream end ?

Answer 81

The order of milliseconds

Question 82

What detects the rise in pressure of both the primary shock wave and the reflected wave ?

Answer 82

The sensors

Question 83

What are the sensors, exactly ?

Answer 83

Piezoelectric transducers

Question 84

Why is a oscilloscope of bandwidth of 1 MHz required ?

Answer 84

The rist time of the oscilloscope shoud be few microseconds, since the duration of the shcok wave is 1 millisecond

Question 85

Where is the data collected by the sensors recorded ?

Answer 85

Digital CRO (Cathode Ray Oscilloscope)

Question 86

What are the general gases used ?

Answer 86

Helium - Driver gas Argon - Driven gas

Question 87

What kind of temperature can this combination generate ?

Answer 87

Temperatures above 900K

Question 88

What are Rankine - Hughoniot equations ?

Answer 88

The equations of conservation of mass, momentum and energy as applied to shock waves