In the simple words, the
resistance capacity of a liquid or fluid material is defined by its viscosity.
So, it’s nothing but a mechanical friction between molecules in motion. Higher
viscosity means higher resistance to deformation of the liquid because of
mutual attraction of the molecules. Viscosity is denoted by a symbol η (eta) –
a ratio of the shearing stress to the velocity gradient in a fluid.
Consider an example of viscosity
with water and honey, water flows relatively freely than honey; it is because
honey has the higher viscosity than water. There are various industrial or
commercial applications viscosity measurement devices that help you understand
the flowing nature and motion of a particular material in a given temperature.
Viscosity is a subject of Rheology
The flowing behaviors of
different materials or matters are studied under Rheology. It’s actually a
science of deformation and flow of different matters that are put under the controlled
testing conditions.
It considers the matters’ liquid,
soft solid or semi-liquid state to see their flow under different
circumstances. Soft matters like polymer, blood, sludge, silicates, and other
biological materials are considered for viscosity measurement. There are
basically two types of viscosity – Dynamic or absolute viscosity and kinematic
viscosity.
In industrial sphere, Rheology is
considered to understand how a fluid material is rubbed, pumped, molded,
coated, mixed, sprayed, extended, extruded, chewed, swallowed, transported,
stored, heated, cooled, and aged. So you can understand how comprehensive
industrial applications are associated with rheology.
Measurement of viscosity and industrial applications
The readings of viscosity vary
with different fluid and soft liquid matters. There are different ways to
measure viscosity starting from capillary tube methods that were used in early
of the 20th century. Now there are many manufacturers of viscometers
that come up with different techniques including nanotechnology and digital scanning.
Capillary viscometer uses some specially
designed tubes in which a volume of liquid passes through. It shows the flowing
speed and space variation under a shear stress (the force required to move
matter within an area).
Zahn Cup is a high shear
viscometer that has a small hole in the bottom to measure the flowing speed of
a liquid. This device is often used for quality control in the paint industry.
Falling sphere viscometer helps
you to record a specified point by dropping a fluid sample through it. This
device is widely used to see the quality of fuel in the engines.
Vibrational viscometer helps to
measure an oscillating electromechanical resonator that is immersed in a particular
fluid. On the other hand, rotational viscometer can measure the torque that can
turn an object into the fluid form. It’s very much used in production labs to
scale a fluid quality.
New technology used in high shear viscometer
The advanced viscometer
technology is being used to measure fluid viscosity with higher accuracy,
better repeatability, and automation facility even for a small sample volume. The
high shear rate is easily drawn to assist industrial processes. For example,
viscometer/rheometer-on-a-chip (VROC) technology has revolutionized the way
viscosity is measured for industrial applications ranging from fuel, paint,
plastic, toothpaste to food products and pharmaceutical industries.
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