In fluid dynamics, a Cross fluid is a type of generalized Newtonian fluid whose viscosity depends upon shear rate according to the Cross Power Law equation: where
is viscosity as a function of shear rate,
is the infinite-shear-rate viscosity,
is the zero-shear-rate viscosity,
is the time constant, and
is approached at very low shear rates, while the infinite shear viscosity
is approached at very high shear rates.
, the fluid exhibits shear thinning (pseudoplastic) behavior where viscosity decreases with increasing shear rate; when
, the fluid displays shear thickening (dilatant) behavior where viscosity increases with shear rate.
It is named after Malcolm M. Cross who proposed this model in 1965.