Effect of size distribution on azimuthal asymmetry and ring viscosity. Upper frames: A_asym and ∆θ_min in the case of strong (r_h = 0.80) and weak (r_h = 0.61) self-gravity. The width of size distribution is varied, while keeping τ_dyn and Σ fixed by a suitable choice of R_min and R_max (see Appendix A). Filled circles indicate overstable simulations. Lower frames: total viscosities and various contributions to viscosity as a function of W, for weak (left) and strong (right) self-gravity. Box symbols denote ν_grav calculated from density autocorrelation function (see Appendix B). The viscosities are normalised with ΩR_o² where R_o in the case of size distribution denotes the identical particle size, R, that yields the same τ_dyn and Σ. Dashed lines in the right axis indicate the ν_ɡrav from Daisaka et al. (2001) viscosity formula, Eq. (14). In all simulations τ_dyn = 1, ϵ_n = 0.1.