Fluid Mechanics

Question 1

Liquids are considered…

Answer 1

… incompressible

Question 2

Gases are considered…

Answer 2

… compressible

Question 3

Viscosity

Answer 3

a measure of resistance to flow

Question 4

Dynamic (absolute) viscosity

Answer 4

ratio of shearing stress to rate of shearing strain

Question 5

Newtonian fluids

Answer 5

rate of shearing strain is constant for a given temperature

Question 6

The viscosity of most liquids decreases significantly with…

Answer 6

… increase in temperature

Question 7

The viscosity of most gases increases mildly with…

Answer 7

… an increase in temperature

Question 8

Fluid

Answer 8

a substance that will deform readily and continuously when subjected to shear force

Question 9

Absolute pressure

Answer 9

measured from a vacuum

Question 10

Gage pressure

Answer 10

uses atmospheric pressure as datum

Question 11

Vacuum

Answer 11

negative gage pressure

Question 12

In a capillary tube, a liquid will rise when…

Answer 12

… adhesive forces dominate

Question 13

In a capillary tube, a liquid will fall when…

Answer 13

… cohesive forces dominate

Question 14

The center of pressure is always…

Answer 14

… below the centroid except when the surface is horizontal

Question 15

Buoyant force is equal to…

Answer 15

… the weight of the fluid displaced by the object

Question 16

Inviscid

Answer 16

viscosity is assumed negligable

Question 17

The sum of the hydraulic grade line and velocity head is the…

Answer 17

… energy grade line

Question 18

Reynolds number (Re)

Answer 18

ratio of inertial forces to viscous forces in fluid flow

Question 19

Moody diagrams are used to…

Answer 19

… determine the friction factor

Question 20

Hazen-Williams equation

Answer 20

used to determine head loss in a system

Question 21

For pipes in series…

Answer 21

… volumetric flow rates and head loss are equal

Question 22

For pipes in parallel…

Answer 22

… total volumetric flow rate and head loss are additive

Question 23

Pumps

Answer 23

add energy to liquid systems

Question 24

Compressors

Answer 24

add energy to gases

Question 25

Dynamic pump

Answer 25

energy is added by a set of blades (impellers, vanes) that are attached to a rotating shaft turned by a motor

Question 26

Centrifugal pump

Answer 26

impeller attached to a rotating shaft with fixed housing

Question 27

Pump efficiency

Answer 27

ratio of power gained by fluid to shaft power delivered to pump

Question 28

Pumps in a parallel configuration have...

Answer 28

... equivalent head delivered, but total volumetric flow rate is calculated as the sum of the individual flow rate delivered by each pump

Question 29

Cavitation

Answer 29

system pressure is less than or equal to the vapor pressure of the liquid, causing the liquid to form small bubbles of vapor which reduce pump efficiency

Question 30

Impulse turbine

Answer 30

low-discharge, high-head devices in which high-speed jets of water impact bucket-shaped vanes to rotate turbine

Question 31

Froude number (Fr)

Answer 31

ratio of inertial forces to gravitational forces

Question 32

Critical flow occurs when...

Answer 32

... Fr = 1

Question 33

Hydraulic jump

Answer 33

occurs when flow transitions from supercritical to subcritical flow (often seen under sluice gates)

Question 34

Mannings equation

Answer 34

expresses stream velocity during uniform flow

Question 35

Weirs are used to...

Answer 35

... determine flow rate in open channels

Question 36

Darcy-Weisbach

Answer 36

Used to calculate head loss due to friction