Hello everyone,

I have been working on the effect of elasticity in RT type drips. To do this I have run some simple tests checking the results of the models through the topography and the maximum value of the second invariant of the deviatoric stress tensor \sigma'^{2nd}. However, the results are not in agreement with published results.

I tried calculating \sigma'^{2nd} using the full deviatoric stress tensor (2\eta\dot{\epsilon_{ij}}+\sigma_{ij_{elastic}}) using its components to calculate the invariant, and I also calculated \sigma'^{2nd} from the principal stresses using the recent PR for their visualisation, but both results are off. Also, the topography which comes directly from ASPECT’s solution tends to produce more surface deflections than the expected.

I am wondering if this difference is produced by the formulation of the effective viscosity: \eta_{eff}=\eta\frac{\Delta t^{e}}{\Delta t^{e}+\frac{\eta}{\mu}} , which is constant throughout the entire model while for timescales comparable or grater than the relaxation time \frac{\eta}{\mu}, the effective viscosity should approach the “true” viscosity with a formulation such as: \eta_{eff}=\eta-(\eta-\eta_{eff_{0}})e^{-\frac{\mu}{\eta}t}.

I would like to know if this is a simple thing to test maybe by modifying the equation for \eta_{eff} in a material model plugin or if there are more difficulties.

Thanks a lot!

Daivid