Viscometers are instruments designed to measure the viscosity of a fluid. Imagine a viscometer
that applies a shear (tangential force) to a fluid, and measures the force required to apply this
shear (the shear stress). Example data from a viscometer is shown below, where the shear stress
as a function of the velocity gradient (here, the rate of shear strain) is tabulated. The data below
is for different types of honey adapted from:
Santos, Francisco Klebson & Filho, Antonio & Leite, R.H.L. & Aroucha, Edna & Santos,
Andarair & Oliveira, Thiago. (2014). Rheological and some physicochemical characteristics of
selected floral honeys from plants of caatinga. Anais da Academia Brasileira de Ciências. 86.
10.1590/0001-3765201420130064.
Shear stress as a function of strain rate for different types of honey
shear rate (1/s) shear stress (Pa)
croton
camprestris
0
10
20
30
40
CHE330, Fall 2023
50
60
70
80
90
0
18
40
52
60
91
105
130
145
170
cobretum
leprosum
0
48
105
HW#2
149
199
255
310
351
385
444
mimosa
tenufiora
0
88
178
249
344
420
a. [5] Plot the data on a graph of shear stress as a function of shear rate. Since you have
individual data points, plot individual points. You may use any type of software, but Excel is
520
597
669
771
recommended. Make sure your plot shows data points, legend, and has labelled axes
including units.
b. [2] What type of fluid is honey (Newtonian, shear thinning, shear thickening)? Explain
your answer using your graph.
c. [5] If a fluid is Newtonian, you can fit a linear trendline through the data from part a,
forcing the intercept through the origin. Show the trendline and the equation of the trendline
on the plot (note that the intercept of the trendline must be zero- you can force it through zero
in the trendline setup in Excel). Determine the viscosity of each type of honey in cP.
Fig: 1