mach number

Mach number is a measure of speed. When we say an aircraft is flying at Mach 1, it means that the speed of the vehicle is 343 m/s.

Mach number is the ratio between the true airspeed of the aircraft to the local speed of sound. Since it is a ratio, it is a dimensionless quantity. The word 'local' has a significant importance in the definition. Local means the immediate surrounding of the aircraft, i.e, in the same medium.

M=V/a,

where M is Mach number, V is the speed of the aircraft and a is the speed of sound in the same medium.

(or)

v=speed of the any object, 'a' is the speed of sound.

Simple classification of Mach regime is as follows:

Mach 0.3 > Low subsonic

Mach 0.3 — 0.8 = High subsonic

Mach =1= sonic regime(region).

Mach 0.8 — 1.2 = Transonic

Mach 1.2 — 5.0 = Supersonic

Mach 5.0 < Hypersonic.

The highest Mach number achieved by a manned vehicle is 3.2 by the U.S Airforce SR-71 .

• for eg:

Speed of Sound in Air is 343 meters/second.

Lets say the speed of the aircraft is 378 meters/ second.

So Mach number will be 378/343, i.e 1.10

It is usually denoted as Mach 1.01

So, when someone says the speed of the aircraft is Mach 2, it means the speed of the aircraft is 343 m/s multiplied by 2, i.e 686 m/s.

And 686 m/s roughly translates into 2470 k mph.

like so we can calculate the mach number for an aircraft.

thank you,

Edit, suggestions, corrections and appreciation are most welcome.

yours Chandra shekar.