  The paper presents results of numerical experiments performed to evaluate the
effective viscosity of a fluid-proppant mixture, used in hydraulic fracturing.
The results, obtained by two complimenting methods (the particle dynamics and
the smoothed particle hydrodynamics), coincide to the accuracy of standard
deviation. They provide an analytical equation for the dependence of effective
viscosity on the proppant concentration, needed for numerical simulation of the
hydraulic fracture propagation.
