1. A liquid has a mass density of 1550 kg/m3 and calculate specific gravity.
a) 1.55
b) 1.56
c) 1.50
d) 1.54
Explanation: Given data: Mass density = 1550 kg/m3
2. A liquid has a mass density of 1550 kg/m3 and calculate specific volume?
a) 6.51 × 10-5 m3/N
b) 6.78 × 10-5 m3/N
c) 6.45 × 10-5 m3/N
d) 6.57 × 10-5 m3/N
Explanation: Specific volume = 1/(Specific weight)
= 1/(1.52×104 N/m3)
= 6.57 × 10-5 m3/N.
3. If the equation of a velocity profile over a plate is v = 5y2 + y (where v is the velocity in m/s) determine the shear stress at y = 0. Given the viscosity of the liquid is 8.35 poise.
a) 0.830
b) 0.832
c) 0.835
d) 0.834
Explanation: Given Data: Velocity profile v = 5y2 + y;
μ = 8.35 poise
Substituting y=0 on the above equation, we get shear stress at respective depths.
τ = 0.835
4. Refer to Q3 and determine the shear stress at y =7.5cm.
a) 1.46 N/m3
b) 1.45 N/m3
c) 1.40 N/m3
d) 1.43 N/m3
Explanation: Given Data: Velocity profile v = 5y2 + y;
μ = 8.35 poise
Substituting y=7.5 on the above equation, we get shear stress at respective depths.
τ = 1.46 N/m3.
5. “Mach is the Dimensionless quantity”.
a) True
b) False
Explanation: In fluid dynamics, the Mach number (M or Ma) is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound.
where:
M is the Mach number,
u is the local flow velocity with respect to the boundaries (either internal, such as an object immersed in the flow, or external, like a channel), and
c is the speed of sound in the medium.
6. Which of the following fluid flow can form “eddies”?
a) Streamline flow
b) Laminar flow
c) Turbulent flow
d) Non-turbulent flow
Explanation: The slower the flow the more closely the streamlines represent actual motion. Slow fluid flow is therefore called streamline or laminar flow. In fast motion, fluid particles frequently cross and recross the streamlines. This motion is called turbulent flow and is characterized by formation of eddies.
7. What do you mean by “u” in the following equation of Reynolds number and for what type of conduit is it applicable?
\(R_e = \frac{Duρ}{\mu}\)
a) Fluid viscosity, Stirred vessel
b) Average linear velocity, Pipe
c) Average linear velocity, Stirred vessel
d) Fluid viscosity, Pipe
Explanation: A parameter used to characterise fluid flow is the Reynolds number. For full flow in pipes with circular cross-section, Reynolds number Re is defined as:
\(R_e = \frac{Duρ}{\mu}\)
where D is pipe diameter, u is average linear velocity of the fluid, ρ is fluid density, and μ is fluid viscosity. For stirred vessels there is another definition of Reynolds number:
\(R_{ei} = \frac{N_i D_i^2 \rho}{\mu}\)
where Rei is the impeller Reynolds number, Ni is stirrer speed, Di is impeller diameter, ρ is fluid density and μ is fluid viscosity.
8. In smooth pipes, Laminar flow is encountered at what value of Reynolds number?
a) More than 2100
b) 2100-4000
c) More than 4000
d) Less than 2100
Explanation: One of the most significant outcomes of Reynolds’ experiments is that there is a critical Reynolds number which marks the upper boundary for laminar flow in pipes. In smooth pipes, laminar flow is encountered at Reynolds numbers less than 2100. Under normal conditions, flow is turbulent at Re above about 4000. Between 2100 and 4000 is the transition region where flow may be either laminar or turbulent depending on conditions at the entrance of the pipe and other variables.
9. What do you mean by incompressible flow?
a) Temperature is constant
b) Density is constant
c) Pressure is constant
d) Velocity is constant
Explanation: In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric flow) refers to a flow in which the material density is constant within a fluid parcel an infinitesimal volume that moves with the flow velocity.
10. Is water incompressible?
a) True
b) False
Explanation: An important concept in fluid mechanics is that liquids, like water and oil, cannot be compressed much when you push down on them in an enclosed container. So, liquids are considered to be incompressible fluids.