Fluid Mechanics Multiple Choice Questions on “Flow through Nozzles”.
1. When a gas is pushed through a pipe, the gaseous molecules are _________ by the pipe’s walls
a) Attracted
b) Absorbed
c) Deflected
d) Dissipated
Answer: c
Clarification: This is because there is no attractive force present in the tube for the process of attraction to occur. Also, the surface of pipes is not an absorbing one, hence absorption is also ruled out. A pipe is not capable of dissipation of the molecules. Hence, the right option is deflected.
2. If the speed of sound is much ________ than that of the gas, the gas density will stay constant.
a) Smaller
b) Larger
c) Equal to
d) Non-existent
Answer: b
Clarification: This is because only with speed of sound Is larger, it’ll be able to compensate for the speed of gas. Under such situations, the gas density will be able to stay constant. If they are equal, density will get compressed.
3. Isentropic nozzle flow states about the movement of a gas or fluid through a narrow orifice without an increase or decrease in ___________
a) Pressure
b) Energy
c) Displacement
d) Entropy
Answer: d
Clarification: Entropy is defined as the measure of degree of randomness. It is a thermodynamics quantity. As this nozzle flow deals with thermodynamics, entropy is the right choice. The other options are not parameters of entropy.
4. In fluid dynamics, the velocity of the fluid in the stagnation point is
a) Zero
b) Infinite
c) Non-existent
d) Negative
Answer: a
Clarification: Stagnant point is a point where there is no movement of the fluid. When there is no movement, the velocity will be 0. Hence the answer is 0.
5. The stagnation state is obtained after a _____________ to zero velocity.
a) Accelerating
b) Decelerating
c) Equilibrium
d) Exponential increase
Answer: b
Clarification: Initially the flow has a velocity. In the stagnant state, the velocity is 0. For this to happen, there should be a deceleration of the velocity. Hence, deceleration is the answer.
6. To refrain from separation in subsonic nozzles, the expansion angle must not be more than _____
a) 10 degrees
b) 20 degrees
c) 30 degrees
d) 40 degrees
Answer: a
Clarification: If the angle is more than 10 degrees, there will be a drift amidst the nozzle. At any angle more than 10 degrees, this separation will occur. But the minimum value is 10 degrees. So, the answer is 10 degrees.
7. Gas flows through the nozzle from an area of _____ pressure (called the chamber) to one of _____ pressure
a) High, low
b) Low, high
c) Same, same
d) Constant, Infinite
Answer: a
Clarification: Anything that flows or runs moves from a region of higher value to lower value. We can take the example of any physical parameter like pressure, altitude etc. Hence, here the gas will flow from high to low pressure regions.
8. Converging-diverging nozzle is also known as __________
a) Pascal nozzle
b) Bernouille’s nozzle
c) Toricelli’s nozzle
d) de Laval’ nozzle