# Pulp & Paper Questions and Answers – Flow of Liquids

This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Flow of Liquids”.

1. In order to simplify the mathematical development, flow is often considered in rectangular cross section pipe.
a) True
b) False

Explanation: The flow of liquids in pipes can be difficult to describe mathematically. To simplify the mathematical development, flow is usually considered in circular cross section pipe.

2. The ___________ is an crucial parameter utilized to predict the flow pattern in a pipe.
a) Plank’s number
b) Reynold’s number
c) Kraft’s number
d) Sherwood number

Explanation: It is defined as the ratio of inertial forces to viscous forces and consequently quantifies the relative crucial of these 2 types of forces for given flow conditions.

3. If the Reynolds number is below 2000, the flow tends to be __________
a) Turbulent
b) Laminar
c) Transitional
d) Can’t be predicted

Explanation: It is a flow regime characterized by high momentum diffusion and less momentum convection. Whenever a fluid is flowing through a closed channel such as a pipe or between 2 flat plates, either of 2 types of flow may occur depending on the velocity and viscosity of the fluid.

4. If the Reynolds number is above 2000, the flow tends to be ___________
a) Turbulent
b) Laminar
c) Transitional
d) Can’t be predicted

Explanation: Turbulent flow is a flow regime characterized by chaotic changes in pressure and flow velocity. In unsteady vortices appear on many scales and interact with each other. Drag due to boundary layer skin friction inc.

5. The addition of a small amount of ___________ to H2O may actually reduce friction compared to H2O alone.
a) Pulp
b) Lignin
c) Fiber
d) Polymer

Explanation: The addition should be done on the order of 0.3% consistency although it can be higher at higher flow velocities, so it could actually reduce friction compared to H2O alone.

6. What is the name of the equation?

Q = (πΔPr4) / (8µL)

a) Darcey equation
b) Poiseuille law
c) Reynolds equation
d) Sherwood law

Explanation: The Hagen–Poiseuille equation also called as the Hagen–Poiseuille law, is a physical law that gives the pressure drop in an incompressible and Newtonian fluid which is flowing through a long cylindrical pipe in laminar flow of constant cross section.

7. What is the name of the equation?

h = (fvL) / (2Dg)

a) Darcey equation
b) Poiseuille law
c) Reynolds equation
d) Sherwood law

Explanation: It’s a constitutive equation that describes the flow of a fluid through a porous medium. It’s based on the results of experiments on the flow of H2O through beds of sand, forming the basis of hydrogeology, a branch of earth sciences.

8. What does ub stands for?

Re = (Dubρ) / µ

a) Initial velocity
b) Final velocity
c) Bulk velocity
d) Blocking velocity

Explanation: If the flow regime is laminar the problem still exists of trying to represent the “average” velocity at any given cross-section since an average value is utilized in the fluid flow equations. For fluid flow in a pipe or duct, the average flow velocity, given by V = ṁ/ρA.

9. For Reynolds number below 2000, f has been empirically shown to be equal to 64/Re.
a) True
b) False

Explanation: In case of Laminar flow, it’s a consequence of Poiseuille’s law from an exact classical solution for the fluid flow that where Re is Reynold’s number and where µ is the velocity of the fluid and is known as kinematic viscosity.
fD =64/Re, Re=V.D/v.

10. ___________ is the sudden change in pressure cautilized by a column of H2O that suddenly changes velocity (as when a valve is closed).
a) H2O hammer
b) Globe hammer
c) Needle hammer
d) Air check hammer

Explanation: It’s a pressure surge or wave cautilized when a fluid generally a liquid but sometimes also a gas in motion is forced to stop or change direction suddenly (momentum change). It’s also known as hydraulic shock.

Sanfoundry Global Education & Learning Series – Pulp and Paper.
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