A fluid whose consistency is a function of shear stress, and the shear rate-shear stress relationship is non-linear. The non-Newtonian class of fluids can be further divided in pseudo-plastic, dilatant, Bingham plastic, and thixotropic categories. Examples of non-Newtonian fluids are highly viscous and complex polymers, drilling mud gels, cement, high-density sand slurries and foam.