to the standard viscosity parameter $\alpha_{\nu}$ proposed by @shakura73. Assuming $\alpha_{\nu} \approx 0.01$ [@armitage11], would correspond to an $\alpha_{\rm SPH}$ of roughly 0.02 in our reference model ($\alpha_{\rm SPH} \propto \sqrt[3]{N_{\rm disc}}$), which is too low for numerical reliability. We therefore set $\alpha_{\rm SPH}$ initially to 0.1, as was also done in e.g. M09 and @rosotti14. We have implemented the viscosity switch proposed by @morris97 in Gadget2[^4]. In this treatment of the viscosity every particle has its individual viscous parameter $\alpha_{\rm SPH}$ (and $\beta_{\rm SPH}=2\alpha_{\rm SPH}$), which is important because we simultaneously need a low value of $\alpha_{\rm SPH}$ in the disc and a high value of $\alpha_{\rm SPH}$, up to 1, to resolve the shock in front of the disc. In the SPH code Fi, the viscosity remains constant throughout the simulation at a value of $\alpha_{\rm SPH} = 0.1$. We have adopted $\beta_{\rm SPH}=1$ for Fi. With these values we minimize the viscous stresses in the disc, which due to the low relative velocities are dominated by the first order $\alpha_{\rm SPH}$ term, while preventing particle interpenetration in the strong accretion shock. We have tested lowering the $\beta_{\rm SPH}$ value below the adopted value and found that it 