The so-called Newtonian fluid generally refers to a fluid whose viscosity η is constant at any given temperature and at a low or medium shear rate, also known as a true liquid. But the so-called Newtonian liquid.
This fluid can be induced to flow by any minimal force applied to it. The rheological curve of Newtonian fluid is shown in line A in Figure 19-3. This is a straight line through the origin in which the shear rate is proportional to the magnitude of the shear stress. That is to say, it will flow when force is given, the greater the force acting on the fluid, the greater the velocity of the fluid flow, and they are proportional. The slope of the line is related to the viscosity of the fluid.
Figure 19-3 Flow curves of various heart flow variants
A-Newtonian fluid, B-pseudoplastic fluid, C-expansive fluid, D-plastic fluid, E-plastic fluid with yield value: F-expandable fluid with yield value.
In the figure, t0 is the yield value, and the dotted line indicates the apparent viscosity corresponding to point x on curve B and point y on curve F.
Substances belonging to this type of fluid include water, solvents, mineral oil, low-viscosity binders, and some liquid (solvent-based) inks with relatively low viscosity.
Substances with a viscosity of 0-100 poise can generally be regarded as Newtonian fluids.
