the calculation of pressure losses through pipes, the determination of pump sizes, the
calculation of hydraulic forces, etc. Thus, it is helpful for the engineer to have a physical
awareness of viscosity and a background in how viscosity is measured. The
measurement of viscosity is generally made with a device known as a viscometer.
There are several methods of determining viscosity, one of which will be demonstrated
in this experiment, the Falling Ball Viscometer.
It is worth noting that viscosity is a measure of relative fluidity at some definite temperature.
Since viscosity varies considerably with temperature, it is essential that the fluid be at a
constant temperature when a measurement is being made. This viscosity can be
measured by several different standardized methods or tests. However, the scope of this
experiment will not include the measurement of temperature effects on fluid viscosity.
Falling Sphere Viscometer
Falling Ball Viscometer
2 unknown liquids.
Fill the cylinder with the liquid of unknown viscosity all the way to the top. Drop the sphere
into the liquid and nut and adapter assembly is tightened on the flange of the tube until
secure. Make sure that the air and gas bubbles should be vented before any readings are
taken. The ball is released by turning the knob to raise the screw. The time of descent
between the two sets of fiduciary lines is measured with a stop watch. Repeat
measurements thrice and take an average reading for the time of descent.
For a falling ball viscometer, the viscosity is calculated by the simple formula:
= Absolute or dynamic Viscosity centipoises (cp);
= Density of the sphere(gms/mL) = 8.02 for stainless steel ball;
= Density of the liquid (gms/mL);
= Time of descent (minutes);
= Viscometer Constant (Value of K is: 0.3 for size 1 or 3.3 for size 2 or 35 for size