Dilatant fluids are similar to pseudoplastic systems in that they show no yield stress but their apparent viscosity increases with increasing shear rate; thus these fluids are also called shear-thickening.
At rest, the voidage is minimum and the liquid present is sufficient to fill the void space.
At low shear rates, the liquid lubricates the motion of each particle past others and the resulting stresses are consequently small.
At high shear rates, on the other hand, the material expands or dilates slightly (as also observed in the transport of sand dunes) so that there is no longer sufficient liquid to fill the increased void space and prevent direct solid-solid contacts which result in increased friction and higher shear stresses.
This mechanism causes the apparent viscosity to rise rapidly with an increasing rate of shear.
It is one of the Non-Newtonian fluids which do not obey the Newtonian equation
The value of n > 1 and B = 0 for these fluids
The viscosity (μ) is not constant and depends on how fast the fluid is deforming
These are called shear thickening fluids because the faster the deformation occurs the more the viscosity increases