Rheology- Part 2

* A rheofluidifiant or pseudo-plastic fluid
This type of fluids [or fluid mechanics] is the case of polymers in a solution [or polymeric behavior in solutions] . The viscosity decreases when the gradient of speed rate of change increases with respect to time* (as the function y=1/x)

* A shear thickening fluid.
This fluid is not common. It is the contrary that opposite of a pseudo-plastic fluid: the viscosity increases when the gradient of speed* increases. It This is the case of with some (types of) honey.

* A viscoplastic fluid
in this case, the flow takes place only for some certain values [conditions?] of the constraint to give impart [=apply] on a fluid, called (the) yield stress. After this constraint, the fluid has the behavior of a rheofluidifiant fluid.
But, some materials have, after the yield stress, the behavior of a nNewtonian fluid. It This is the case of the with mayonnaise for example.

So for non-Newtonian fluid dependent on time, we need to talk to the thixotropy. And it is more complicated.

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*Similar clarification about avoiding using "speed" since it's the scalar quantity of velocity, which is a first derivative (of distance), and a "change in slope/gradient of speed" is a second derivative, so it's better to keep it as "rate change with respect to time".

Rheology- Part 2

* A rheofluidifiant or pseudo-plastic fluid
This type of fluids is the case with polymers in solution. The viscosity decreases when the gradient of speed increases (as a function of y=1/x)

* A shear thickening fluid.
This fluid is not common. It is the opposite of a pseudo-plastic fluid: the viscosity increases when the gradient of speed increases. It is the case with some honey.

* A viscoplastic fluid
In this case, the flow takes place only for some values of the constraint to give on a fluid called yield stress. After this constraint, the fluid has the behavior of a rheofluidifiant fluid.
But, some materials have after the yield stress the behavior of a newtonian fluid. It is the case with the mayonnaise for example.

So for non Newtonian fluid dependent on time, we need to talk about thixotropy. And that is more complicated.

Très bien comme toujours, Marie !