  In this letter, following an extensive experimental validation, we perform
constant-volume shearing simulations of non-Brownian granular suspensions using
the discrete element method coupled with the lattice Boltzmann method. We
choose a wide range of solid fractions, shear rates, fluid viscosities,
particle sizes, and inter-particle frictional coefficients to obtain a scaling
solution for the viscous behavior of suspensions in both dilute and dense
regimes. This letter demonstrates that, with a proposed dilute-dense
transitional solid fraction, $\phi_d$, there exists a strong correlation
between the inverse relative viscosity and the shear stress. This work
incorporates both the $\phi$-dependence and the $\dot{\gamma}$-dependence of
suspension viscosity in a universal framework, which provides a scaling
solution for granular suspensions across dilute and dense regimes and sheds
light on the dilute-dense transition mechanisms.
