Mer331 Lab – Week 2 - Viscosity

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Mer331 Lab Week 2 - Viscosity

• Background Viscosity
• A fluid is a state of matter that does not
  permanently resist shear and the resistance to
  deformation (shear stress) is a function of the
  rate of deformation (shear rate)
• Rheology science of deformation
• Viscometry measurement of rheological
  properties
• Viscosity is the property of a fluid that resists
  deformation
• molasses vs water,
• molasses in January vs molasses in July.
• Newton Law of Viscosity (for Newtonian fluids)

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Background Viscosity
Shear Thickening
Shear stress as a function of deformation
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Background
Oobleck shear thickening
http//io9.com/5715076/nonnewtonian-fluids-the-we
irdest-liquids-youve-ever-seen
 http//en.wikipedia.org/wiki/Bartholomew_and_the_
Oobleck
http//www.youtube.com/watch?vyHlAcASsf6U
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Background
Ketchup, Toothpaste shear thinning
Leaping Shampoo!
Versluis M, Blom C, Meer D, Weele K, Lohse D
(2006) Leaping Shampoo and the Stable Kaye
Effect. Journal of Statistical Mechanics Theory
and Experiment 2006P07007.
http//www.youtube.com/watch?vGX4_3cV_3Mw
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Background Viscosity Units
Absolute (or Dynamic) Viscosity, ? Units 1
Poise 1 g/(cm sec) 1 Pa sec 1 kg/(m sec) 1
N sec/m2 1 Poise 100 cP 0.1 Pa
sec Kinematic Viscosity ? ?/? Units 1 stoke
1 cm2/sec 0.0001 m2/sec
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Techniques for Measuring Viscosity

• Capillary Viscometers
• Rotary Viscometers
• Falling Object Viscometers
• And many others.

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Capillary Viscometers

• Capillary Viscometers
• Measure the flow rate of a fixed volume of fluid
  through a small orifice
• From laminar flow theory we can relate the flow
  rate, pressure drop to viscosity
• ? Ktime
• K is a calibration constant
• Time is measured in seconds
• ? is given in cSt

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Rotary Viscometers

• Use the torque on a rotating shaft to measure a
  fluids resistance to flow
• ? F torque
• F is a calibration constant which you look up in
  the instrument manual

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Falling Object Viscometers

• Apply Fma
• At terminal speed a0
• FG FB FD
• FG mg rpD3g/6
• FB rfluidpD3g/6
• The drag on a sphere depends on the flow field
• .

FB Buoyancy
FD Drag
FG Weight
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Falling Object Viscometers

• The drag on a sphere depends on the flow field
• Reynolds Number
• For Stokes Flow Re lt 0.1
• Therefore
• Restrictions terminal velocity, Re lt 0.1

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Gilmont Viscometer

• m Kt(rball-rfluid)
• K 35
• Rball,ss 8.02 (gm/ml)
• Rball,glass 2.53 (gm/ml)
• m in Cp
• t in minutes

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Lab Write Up

• You will write a full lab report. Review the
  information on the course webpage
• http//engineering.union.edu/andersoa/mer331/MELa
  bReports.htm
• Include detailed information on the uncertainty
  analysis
• Table of uncertainty values for each thing you
  measure (i.e. mass, volume etc).
• Report all data with an uncertainty value
• Include (hand written) derivation of uncertainty
  equations with a sample calculation in an
  appendix.
• See handout on lab report expectations.