An essential closure of hydraulic fracturing models is the solution of the momentum equation for flow between plane parallel walls. Newtonian or simple power-law rheology is usually assumed. In real treatments, fracturing fluid often has more complicated rheology, such as Carreau. An earlier introduced modification to the power-law model enables a fair approximation to Carreau rheology. Unlike Carreau, it also enables a closed-form solution for the flow rate between plane parallel walls. The computational cost is, however, considerably smaller than with Carreau. Closed-form solution for the flow rate versus pressure gradient is obtained which is useful in hydraulic fracturing simulations. Compared to simple power-law model, the truncated power-law model improves accuracy of flow computations in small-aperture and large-aperture parts of the fracture, thereby improving the overall accuracy of hydraulic fracturing simulation. (C) 2015 Elsevier B.V. All rights reserved.