P3

Question 1

What is fluid flow primarily concerned with?

Answer 1

Driving forces, resistance (viscous drag force), and energy used.

Question 2

How does moving liquids or gases differ from moving solids?

Answer 2

Fluids do not have a fixed shape.

Question 3

What is another name for streamline flow?

Answer 3

Laminar flow.

Question 4

Under what conditions does streamline flow occur?

Answer 4

At lower values of flow rate and pressure difference.

Question 5

What happens to fluid particles in streamline flow?

Answer 5

Drift velocities of particles are all parallel and in the same sense.

Question 6

What is the velocity of fluid in contact with a static solid surface?

Answer 6

Virtually the same velocity as that of the surface (zero).

Question 7

Why is streamline flow considered the most energy efficient type of flow?

Answer 7

Because it minimizes energy loss.

Question 8

What is turbulent flow characterized by?

Answer 8

Higher flow rates, rotational flows, and chaotic behavior.

Question 9

What is the energy absorption comparison between turbulent flow and streamline flow?

Answer 9

Turbulent flow absorbs much more energy.

Question 10

What makes turbulent flow more complex to model mathematically?

Answer 10

Its chaotic nature.

Question 11

What does viscosity measure in fluids?

Answer 11

Resistance to flow.

Question 12

What causes a velocity gradient in fluids?

Answer 12

Layers of fluid moving at different speeds.

Question 13

What is the equation relating shear stress, dynamic viscosity, and velocity gradient?

Answer 13

F/A = T = n (Au/Ay).

Question 14

What are the units for dynamic viscosity (n)?

Answer 14

Pas.

Question 15

What happens to the onset of turbulent flow for low-viscosity fluids?

Answer 15

It happens sooner.

Question 16

What does the velocity profile look like in a river or pipe?

Answer 16

Curved with a maximum in the center.

Question 17

Fill in the blank: The viscous drag force is defined by _______.

Answer 17

Newton’s law of viscosity.

Question 18

True or False: Turbulent flow is easier to model than streamline flow.

Answer 18

False.

Question 19

What are the effects of sharp bends on streamline flow?

Answer 19

They can cause turbulence.

Question 20

What is the significance of shear stress in fluid mechanics?

Answer 20

It quantifies the internal friction in a fluid.

Question 21

What is a characteristic of Newtonian fluids?

Answer 21

Their viscosity, n, is a constant value at any given temperature and pressure.

Question 22

What defines non-Newtonian fluids?

Answer 22

Their viscosities change in response to shear stress.

Question 23

What are shear thinning fluids also known as?

Answer 23

Pseudoplastic fluids.

Question 24

What happens to pseudoplastic paints when brushed?

Answer 24

They thin and then thicken, preventing running or dripping.

Question 25

What are shear thickening fluids also known as?

Answer 25

Dilatant fluids.

Question 26

How do dilatant fluids respond to slippage in all-wheel drive systems?

Answer 26

They solidify and engage drive to the rear wheels.

Question 27

What is a thixotropic fluid?

Answer 27

A fluid that thins gradually on stirring and slowly resets.

Question 28

Provide examples of thixotropic fluids.

Answer 28

* Yoghurts * Jellies * Colloidal suspensions

Question 29

What is rheopectic behavior?

Answer 29

A time-dependent thickening with shear stress, thinning again when it stops.

Question 30

Which fluid has rheopectic properties that aid in joint lubrication?

Answer 30

Synovial fluid.

Question 31

What are Bingham plastics?

Answer 31

Materials that behave like solids at low shear stresses but flow above a yield stress.

Question 32

List examples of Bingham plastics.

Answer 32

* Toothpaste * Mud * Slurries * Mayonnaise * Butter * Margarine

Question 33

Fill in the blank: Most fluids are _______ which have a constant viscosity.

Answer 33

Newtonian

Question 34

True or False: Rheopectic behavior is common in fluids.

Answer 34

False

Question 35

What is mass flow continuity?

Answer 35

Mass flow continuity states that the mass flow rate must be the same at: * entering the system * crossing every boundary along its length * leaving from its outlet ## Footnote It allows for measurement of mass flow at any point along the flow.

Question 36

What implication does mass flow continuity have for volume flow rate in liquids?

Answer 36

Mass flow rate continuity implies continuity of volume flow rate, Ф, for liquids in pipes, as liquids are nearly incompressible. ## Footnote This means that the volume flow rate remains consistent throughout the system.

Question 37

How does flow rate, Ф, relate to pressure gradient, Ap/L?

Answer 37

Flow rate, Ф, varies in proportion to the pressure gradient, Ap/L, where Ap is the pressure difference and L is the length of the pipe. ## Footnote This relationship is crucial for understanding fluid dynamics in piping systems.

Question 38

What factors increase pressure drop in pipes?

Answer 38

Pressure drop increases if: * viscosity, n, increases * there is turbulence ## Footnote These factors affect the efficiency of fluid transport in pipes.

Question 39

How does pipe radius affect pressure drop?

Answer 39

Pressure drop varies inversely with the 4th power of the pipe radius, r. ## Footnote This means small changes in radius can lead to significant changes in pressure drop.

Question 40

What does Bernoulli's principle state?

Answer 40

Bernoulli's principle applies energy conservation to steady flow systems, represented by the equation: -mv + mgh + pV = a constant value. ## Footnote This principle is fundamental in fluid dynamics.

Question 41

What is the result of dividing Bernoulli's principle equation by mass, m?

Answer 41

The result is: 2 + gh + p/p = a constant value, where p is density. ## Footnote This shows the relationship between velocity, pressure, and height in fluid flow.

Question 42

What happens to pressure, p, when velocity, v, increases according to Bernoulli's principle?

Answer 42

When velocity, v, increases, pressure, p, will automatically drop, provided that height, h, has not changed. ## Footnote This is a key concept in understanding how fluids behave in motion.

Question 43

What creates lift in an aerofoil?

Answer 43

Lift is created because air has to travel further over the top of an aerofoil than underneath it, resulting in a pressure difference. ## Footnote This principle is essential for the flight of aircraft.

Question 44

What is the function of Pitot tubes?

Answer 44

Pitot tubes measure aircraft velocity by converting air speed into a pressure difference. ## Footnote They are vital instruments in aviation for determining speed.

Question 45

Fill in the blank: Pressure drop increases if the _______ increases.

Answer 45

viscosity, n ## Footnote This impacts the efficiency of fluid flow.