1. Incompressible flow is the one in which density is ___________
a) 0
b) constant
c) varies from point to point
d) negligible
Explanation: In incompressible flow, the density remains constant because of which the fluids cannot be compressed and are called as incompressible fluids. Water is the best example of incompressible fluids. But still some extent we can compressible water.
2. In a wind tunnel, the section with minimum area is called as __________
a) exit
b) nozzle
c) inlet
d) throat
Explanation: When the flow enters the wind tunnel (convergent-divergent) with a velocity V1 and pressure P1. The velocity increases and the pressure decreases at the minimum area section called the throat. Pressure is minimum at the throat.
3. In a venturi duct, the pressure at throat is __________
a) lower than ambient pressure
b) equal to ambient pressure
c) greater than ambient pressure
d) 0
Explanation: It is the characteristics of the venturi duct that the pressure at the throat is lower than the pressure at the inlet (ambient pressure). Because of this characteristic, it has many applications in the aerodynamics
4. The carburetor of an automobile engine makes use of _____
a) venturi duct
b) convergent duct
c) divergent duct
d) wind tunnel
Explanation: In venturi duct, the pressure at the throat(p2) is lower than the pressure at the inlet(p1). The pressure difference p2-p1 helps to force the fuel into the airstream and mix it with the airstream downstream of the throat.
5. Which of the following parameter can be measured using venturi?
a) temperature
b) velocity
c) volume
d) density
Explanation: Using venturi, velocity can be measured. We can calculate the pressure difference using venturi. In the duct, we can place pressure gauge which will directly give us the pressure difference (p2-p1). This pressure difference can be related to velocity using Bernoulli’s equation and hence, the velocity can be calculated.
6. The open circuit wind tunnel is similar to venturi duct ______
a) True
b) False
Explanation: In an open circuit wind tunnel, the air is directly drawn from the atmosphere, and again sent back to the atmosphere. Also, the velocity at the inlet is greater than exhaust and the pressure is greater at the exhaust.
7. Which of the following is an application of incompressible flow in a duct?
a) High speed wind tunnel
b) Low speed wind tunnel
c) Flow in air
d) Cannot be said
Explanation: Low speed wind tunnel is a large venturi where the airfoil is driven by a fan connected to some type of motor drive. The wind tunnel fan is similar to the propeller of an aircraft and is designed to draw the airflow through the tunnel circuit.
8. Inside a wind tunnel, the area further decreases from A2 to A3, that section is called as _______
a) Converging section
b) Divergent section
c) Throat section
d) Nozzle
Explanation: The purpose of the diffuser is to reduce the velocity. In order to decrease the velocity, the wind tunnel is designed in such a way that the area in the divergent section decreases and the pressure in this section increases further.
9. The most common device used for measuring air speed is __________
a) altimeter
b) thermometer
c) pressure gauge
d) pitot tube
Explanation: Pitot tube is a tube bent in L shaped. The one end of the pitot tube is exposed to air so that it can directly come in contact with the flow velocity. The pressure inside this tube is used to measure the velocity.
10. The randomness of the molecules gives us ________ pressure.
a) Stagnation
b) Static
c) Dynamic
d) Absolute
Explanation: Static pressure is the measure of purely random motion of the molecules of the gas. It is the pressure which we can feel when we ride along with the gas at the local flow velocity. For reference, we always consider pressure as static pressure.