******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Hi all, I have a few questions regarding spectral vanishing viscosity and hope somebody can help me out. I read in section 9.3.2.2 of Prof. Sherwins book Spectral/hp element methods for computational fluid dynamics that: - only the upper one-third of the spectrum should be treated with SVV - the optimal SVV amplitude level (called diffusion parameter in the user guide) is unknown a priori. Since according to the user guide SVV is activated for modes higher than the product of the cut-off ratio and the expansion order, 1. means the cut-off ratio shouldn't fall below a value of 2/3. I wonder why the default value for all SVV kernels is 0.75 and 2/3? Furthermore, since again according to the user guide, the diffusion parameter is scaled by h/p, how is h evaluated and which value is used for p if different expansions are used for different flow variables? Is p always corresponding to the expansion used for velocity? In section 9.4.2.3 of the book a possible dynamic SVV model formulation is presented. Another question I am interested in, is whether it is possible to activate such a dynamic SVV model within the incompressible N-S solver of Nektar and if not, which procedure would you recommend in order to optimally tune SVV diffusion for a given flow problem? Thanks in advance and all the best Alex Sicher versendet mit [Proton Mail](https://proton.me/).