Fluid Mechanics Multiple Choice Questions on “Stagnation Properties”.
1. __________ is referred as the temperature at a stagnation point in the flow of fluids in fluid mechanics and thermodynamics.
a) Absolute temperature
b) Maximum temperature
c) Stagnation temperature
d) Hydraulic temperature
Answer: c
Clarification: Stagnation temperature is the temperature at the stagnation point of the flow of fluids. In thermodynamics and fluid mechanics, these terms find application. At a stagnation point the speed of the fluid is zero and all of the kinetic energy has been converted to internal energy and is added to the local static enthalpy.
2. In ________ and _______ kind of flow, the stagnation temperature is equal to the total temperature
a) compressible, incompressible
b) stagnated, non-stagnated
c) dynamic, non-dynamic
d) turbulent, passive
Answer: a
Clarification: In compressible and incompressible kind of flow, the stagnation temperature is equal to the total temperature. This occurs at all points on the streamline. Eventually, this leads to the stagnation point.
3. _____ is the law employed in the derivation of stagnation point.
a) Hooke’s law
b) Poisson’s law
c) Second law of thermodynamics
d) First law of thermodynamics
Answer: d
Clarification: First law of thermodynamics is the law employed in the derivation of stagnation point. It states that the change in the internal energy ΔU of a closed system is equal to the amount of heat Q supplied to the system, subtracting the amount of work W done by the system on its surroundings. It is a modified form of the law of conservation of energy.
4. A bimetallic ________ is generally utilized to measure stagnation temperature
a) Transistor
b) Thermometer
c) Diode
d) Thermocouple
Answer: d
Clarification: A bimetallic thermocouple is generally utilized to measure stagnation temperature. However, there must be allowances for thermal radiation. This is done in order to avoid the occurrence of errors.
5. Stagnation point is the point in fluid mechanics where the velocity of the fluid at that point is _____
a) zero
b) infinite
c) constant
d) unity
Answer: a
Clarification: Stagnation point is the point in fluid mechanics where the velocity of the fluid at that point is zero. Stagnation points occur at places where the fluid is brought to a state of rest by an object. They usually exist at the surface of objects.
6. _________ proves that the static pressure is maximum when the velocity is zero
a) Laws of Thermodynamics
b) Bernoulli’s Equation
c) Hooke’s law
d) Principle of continuity
Answer: b
Clarification: Bernoulli’s equation proves that the static pressure is maximum when the velocity is zero. Bernoulli’s principle states that a rise in the speed of a fluid occurs simultaneously with a drop in pressure or a drop in the fluid’s potential energy. It is named after Daniel Bernoulli, who stated it.
7. Total pressure is an addition of static pressure and ______
a) Dynamic pressure
b) Stagnation pressure
c) Fluid pressure
d) Instantaneous pressure
Answer: a
Clarification: Total pressure is an addition of static pressure and dynamic pressure. In incompressible flow, the stagnation pressure is equal to the sum of dynamic pressure and static pressure. So here, stagnation pressure is equal to total pressure.
8. The pressure coefficient at a stagnation point is _____
a) +1
b) -1
c) 0
d) Infinite
Answer: a
Clarification: The pressure coefficient at a stagnation point is unity. This is referred to as +1. A pressure coefficient is a dimensionless number which describes the relative pressures throughout a flow field in fluid dynamics.
9. _________ minus freestream static pressure gives freestream dynamic pressure
a) Stagnation pressure
b) Total pressure
c) Fluid pressure
d) Instantaneous pressure
Answer: a
Clarification: Stagnation pressure minus freestream static pressure gives freestream dynamic pressure. This plays an important role in determining the pressure coefficient. Hence, the pressure coefficient at stagnation points is +1.
10. On a streamlined body fully immersed in a potential flow, there are ____ stagnation points
a) 1
b) 2
c) 0
d) Infinite
Answer: b
Clarification: On a streamlined body fully immersed in a potential flow, there are 2 stagnation points. One point is present near the leading edge. The other point is present near the trailing edge.