rheology
The viscosity of fluids can be determined by applying a
known force and measuring the resultant rate of deformation.
While there are numerous types of rheometer and
viscometer available which operate at atmospheric pressure
over a wide range of shear rates and shear stresses, the
measurement of viscosity at elevated pressures is not
quite so straightforward due to the need for high pressure
containment. Several designs of high-pressure viscometer
exist and each is challenged with the need for adequate
sealing and remote sensors (Isdale, 1976).