What I think you mean is whether we can handle Newtonian and Non-Newtonian fluids; the answer is yes we handle both. The difference is that the Newtonian fluids (think typical fluids like water) behave linearly (i.e. linear viscosity) with respect to how fast they are sheared, and Non-Newtonian (think suspensions like ketchup or paint) change their viscosity in a nonlinear way depending on how fast they are sheared. Pseudo-plastics (shear-thinning) become thinner at a higher shear rate (ketchup), and dilatant fluids (shear-thickening) become thicker as the shear rate increases (paint).
Key terms to look up: power-law, rheology, non-newtonian, herschel-bulkley, carreau fluid