### Mach Number

• Differentiate between various processes of expansion and compression

• Determine the sonic velocity in a fluid.

• Describe the effect of Mach number in flow.

The local speed of sound in an ideal gas is given by:

$c = \sqrt{kRT}$

where,
c = local speed of sound
k = ratio of specific heats = $\dfrac{c_p}{c_v}$
R = specific gas constant = R /(molecular weight)
T = absolute temperature
Mach number is defined as the ratio of the particle (local) speed to the (local) speed of sound. The Mach number can be calculated by:

$Ma =\dfrac {u}{c}$

where:
Ma is the Mach number
u is velocity of the flow and
c is the speed of sound at the given temperature

### Solved Example:

#### 65-1-01

Mach number is significant in: