******************* 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. ******************* Hello Nektar++ community ! Trying to learn how think work, it is not obvious how to solve some laplacians. I did a first go based on https://github.com/ExCALIBUR-NEPTUNE/nektar-diffusion<https://github.com/ExCALIBUR-NEPTUNE/nektar-diffusion/blob/d9d3584530cb60f33892b820970a8bf72c17eb83/src/UnsteadyDiffusion.cpp#L219C9-L220C55>, which let you solve d_t X = - nabla . (D nabla X) + S using the StdRegions::VarCoeffMap varcoeffs; However trying to modify them during the run has no impact. I guess this is because laplacian is defined only at initialisation with the Implicit time integration method (--verbose tells me Helmholtz operator is "Matrix free"), but even using ImplicitFull doesn't seem to see modification in the factors. So I have two related issues : 1. My D is evolving in time, so what would be the correct setup for time integration and/or solver attributes ? 2. I in fact need to solve two (or more) equations with laplacians, different D for each (and one is without temporal dimension nabla^2 X = S), but how do you define two separate Helmhotz solve for different unknown ? Many thanks in advance for your helpful answers, Romain Futtersack