Question 1 - Non-Newtonian Fluids

Question 1

fluid does not follow Newton’s law: viscosity is not constant but dependant upon the shear rate

Answer 1

non-Newtonian fluids

Question 2

shear viscosity for Newtonian fluid

Answer 2

ratio of shear strees to shear rat and hap netween the plates H.

τ = η𝛾

τ = shear stress
η = dynamic viscosity
𝛾 = shear rate

Question 3

shear viscosity for non-Newtonian fluid

Answer 3

η=η𝛾
τ = η𝛾𝛾

τ = shear stress
η = dynamic viscosity
𝛾 = shear rate

Question 4

viscosity decreases when increasing the shear rate.
These fluids display a constant-viscosity value of the viscosity at low shear rate values followed by a decrease of the viscosity when increasing further the shear rate

Answer 4

shear thinning

Question 5

viscosity increases when increasing the shear rate.
These fluids display a constant viscosity value at low shear rate value is followed by an increase of the viscosity when increasing the shear rate.

Answer 5

shear thickening

Question 6

Do not flow is the applied stress is below a critical threshold called yield stress. Above this critical stress, the fluids flow with a shear stress directly proportional to the shear rate

Answer 6

Bingham fluid

Question 7

critical threshold of applied stress needed to make Bingham fluids flow

Answer 7

Yield Stress

Question 8

Shear thinning: ________ decreases when increasing the shear rate.

Answer 8

viscosity

Question 9

Shear thinning: viscosity decreases when increasing the ________.

Answer 9

shear rate

Question 10

Power Law Model equation

Answer 10

η = K𝛾 ^(n-1)

η = dynamic viscosity
K = consistency
𝛾 = shear rate
n = power law index

Question 11

What η represents

Answer 11

shear viscosity

Question 12

What K represents in power law

Answer 12

consistency

Question 13

What 𝛾 represents

Answer 13

Shear rate

Question 14

What n represents in power law model

Answer 14

power law index

Question 15

Cross Model equation

Answer 15

η = (η0 - η∞)/ 1+(K𝛾)^m

η = dynamic viscosity
η0 = zero-shear viscosity
η∞ = infinite shear viscosity
K = time constant
𝛾 = shear rate
m = dimensionless constant used to modulate the transition between the zero shear constant viscosity reion to the shear thinning region

Question 16

What η∞ represents

Answer 16

infinite shear viscosity

Question 17

What K represents in cross model

Answer 17

time constant

Question 18

What η0 represents

Answer 18

zero-shear viscosity

Question 19

What m represents in cross model

Answer 19

dimensionless constant used to modulate the transition between the zero shear constant viscosity reion to the shear thinning region

Question 20

extension of the Cross model with one additional parameter
employed to better describe the transition between constant-viscosity and shear-thinning
region

Answer 20

Carreau - Yasuda model

Question 21

Carreau-Yasuda model

Answer 21

η = (η0 - η∞)/ (1+(K𝛾)^a)^(n-1/n)

η = dynamic viscosity
η0 = zero-shear viscosity
η∞ = infinite shear viscosity
K = time constant
𝛾 = shear rate
n = dimensionless constant used to modulate the transition between the zero shear constant viscosity reion to the shear thinning region
a = additional parameter to smoothen the transition to shear thinning

Question 22

Bingham model

Answer 22

τ = τy + 𝜂𝑝𝛾

np = plastic viscosity
τy = yield stress

Question 23

polymers that do not present a charge on the chain itself

Answer 23

neutral polymers

Question 24

polymers that carry electric charges on the chain

Answer 24

polyelectrolytes

Question 25

poor solvents + neutral polymers

Answer 25

polymer collapses into dense coils

Question 26

θ solvent + neutral polymers

Answer 26

intra-chain interactions are balanced by polymer-solvent interactions. Polymer conformation is a random coil

Question 27

good solvent + neutral polymer

Answer 27

pollymers are swelled in solution. Polymer conformation is a swollen random coil

Question 28

polyelectrolytes with no salt

Answer 28

charges on polymer exert steric repulsion and the polymer conformation is extended

Question 29

Polyelectrolytes with salt

Answer 29

Electric interactions are screened or partially screened and the polymer conformation is in between extended and random coil

Question 30

dilute polymer regime

Answer 30

concentration of polymer in solution is so low that polymer chains do not interact with each other

Question 31

semi-dilute unentangled polymer regime

Answer 31

above a critical concentration value called overlapping concentration polymer chains begin to interact but they are yet to form entanglement

Question 32

semi-dilute entangled polymer regime

Answer 32

polymer chains start to form some entanglements

Question 33

entangled polymer regime

Answer 33

above a critical concentration value called entanglement concentration polymer chains are fully entangled

Question 34

Polyelectrolytes and neutral polymers could span different regimes due to their _____

Answer 34

conformation

Question 35

For a solution of polyelectrolytes with no salt the chain is _______

Answer 35

extended and therefore is easier to interact with surrounding chains

Question 36

For polyelectrolytes the addition of salt causes __

Answer 36

the screening of the electrostatic interactions on the chain and therefore the chain is free to assume a coil like shape

Question 37

refers to the capacity of a liquid to display both viscous and elastic properties

Answer 37

viscoelasticity

Question 38

Why do polymer solutions show shear thinning?

Answer 38

- low values of shear rate, Flow fluid does not deform random coil due to elastic entropy - when molecular conformation of the random coil is constant the drag exerted the solution is constant - above a certain shear rate, the macromolecule is deformed - this causes a reduction in drag exerted by the liquid - the more the shear rate increases the more the polymer deforms thus causing a continuous reduction of the drag

Question 39

the difference between the stress along the flow direction and the one along the shear gradient direction

Answer 39

First normal stress difference

Question 40

the difference between the stress along the shear gradient direction and that along the vorticity direction

Answer 40

Second normal stress difference

Question 41

Equation for first normal stress difference

Answer 41

N1 = τxx - τyy ## Footnote τxx = stress along flow direction τyy =stress along the shear direction

Question 42

Equation for second normal stress difference

Answer 42

N2 = τyy - τzz ## Footnote τyy = stress along the shear direction τzz = stress along the vorticity direction

Question 43

fanning factor equation

Answer 43

16/Re

Question 44

When is fanning factor used?

Answer 44

Power Law model Moody diagram

Question 45

polymers that do no present a charge on the chain itself

Answer 45

neutral polymers

Question 46

polymers that carry electric charges on the chain

Answer 46

polyelectrolytes

Question 47

The elastic components are quantified via:

Answer 47

the storage modulus G' the viscous modulus G''

Question 48

For low frequency values in the SAOS experiment

Answer 48

G' ∝ ω G' ∝ ω^2

Question 49

What SAOS stands for

Answer 49

Small Angle Oscillatory Shear

Question 50

In this experiment, the sample is between to parallel plates. One oscillates which causes a constant small deformation to the sample, while the other is stationary.

Answer 50

Small Angle Oscillatory Shear experiment (SAOS)

Question 51

Re' equation

Answer 51

Re' = ρ V^n-1D^n / 32.17 K^n-1 ## Footnote Re' =/= Re

Question 52

Hedstrom number equation

Answer 52

He = ρ D^2 τy / η

Question 53

What power law model uses ____ instead of Re

Answer 53

Re'

Question 54

Dimensionless number used in the Bingham moody diagram

Answer 54

Hedstrom number ## Footnote Reynolds number used as well

Question 55

low values of________, Flow fluid does not deform random coil due to elastic entropy

Answer 55

shear rate

Question 56

low values of shear rate, Flow fluid does not deform random coil due to ________

Answer 56

elastic entropy

Question 57

when molecular conformation of the random coil is constant the ____ exerted the solution is constant

Answer 57

drag

Question 58

when molecular conformation of the random coil is ____ the drag exerted the solution is constant

Answer 58

constant

Question 59

when molecular conformation of the random coil is constant the drag exerted the solution is ____

Answer 59

constant

Question 60

above a certain ____, the macromolecule is deformed

Answer 60

shear rate

Question 61

above a certain shear rate, the macromolecule is ____

Answer 61

deformed

Question 62

above a certain shear rate, the ________ is deformed

Answer 62

macromolecule

Question 63

why polyelectrolytes span different regimes to neutral polymers

Answer 63

they have different conformations

Question 64

What the addition of salt to polyelectrolytes does

Answer 64

causes the screening of the electrostatic interactions on the chain and therefore the chain is free to assume a coil like shape

Question 65

above a certain shear rate, the macromolecule is deformed. this causes a ____ in drag exerted by the liquid

Answer 65

reduction

Question 66

above a certain shear rate, the macromolecule is deformed. this causes a reduction in ____ exerted by the liquid

Answer 66

drag

Question 67

above a certain shear rate, the macromolecule is deformed. this causes a reduction in drag exerted by the ____

Answer 67

liquid

Question 68

In turbulent region where the fluid is ...... (0

Answer 68

shear thinning

Question 69

In turbulent region where the fluid is shear thinning (0

Answer 69

lower

Question 70

In turbulent region where the fluid is ..... (n>1) the friction factor is higher than the one for a Newtonian liquid.

Answer 70

shear thickening

Question 71

In turbulent region where the fluid is shear thickening (n>1) the friction factor is .... than the one for a Newtonian liquid.

Answer 71

higher