Question

Instructions: In your usual groups complete the question below and submit on or before April 30, 2020. Show all step in deriving your answers. Question 1 a. In concise manner, explain the following terms: Mach number and Critical Velocity (6 Marks) b. At a particular section of a duct air with a static temperature of 32°C and static pressure 85 KN/m flows with a velocity of 375 m/s. Assuming reversible adiabatic flow calculate the velocity and temperature at a section where the static pressure is 120 KN/m and estimate the Mach number at both sections. The specific gas constant for air may be taken as 287 Nm/kg K and y = 1.4. (19 Marks)

Answer 1

[1] Mach number (M) is defined as the local velocity of flow past a surface to the local velocity of sound.

$M=\frac{V}{A}$

Where V is the local velocity of flow and A is the local velocity of sound.

[2] Critical velocity is the velocity of flow at which the flow becomes sonic , i.e its Mach number becomes equal to one.

.i.e $V=A$ , it means that M=1.

c , (2004 > 2=26.53 OV By SFEE blw A ? ☺ nitq e hat ( s 1 Ante Cp (7-12)+ 99 1009( 905 – 331-12)+ 395 162 = 297-29 mle] By eq.& Toz = I2 + b <92 702 = 396.58+ 27 587 277.872 2x1004 Toy = 395.082 K.

• Toz alt ) M2 12 9.3757032 - 170.4) M2 336.58 I M2 = 0.75