On behalf of Gerry Puckett and received on the deprecated mailing list:
I’m writing a paper with Jon Robey for Computers & Fluids that describes the implementation of his VOF interface tracking algorithm in ASPECT in great detail. One of the reviewers wrote
In Section 3.3, the authors describe the use of [the] entropy
viscosity stabilization technique in the energy (or temperature)
equation. … I believe the use of such stabilization method[s,]
akin to artificial diffusion is justifiable only if it does not
significantly change the engineering results of the problem. The
authors need to demonstrate that.
On the related note, the authors also need to show the functional
form of this entropy and its
dependence to the local Péclet number. A comment on how they select
the stabilization parameters
values are also needed for completeness.
Following the discussion in
 Kronbichler, M., Heister, T., Bangerth, W., 2012. High accuracy
mantle convection simulation through modern numerical methods.
Geophysical Journal International 191 (1), 12–29.
we have gone into great detail to address the first sentence in 2. above. In particular, in reference  on page 18 it is stated that
1. ... the constant \alpha_max = 0.026d depends only on the spatial dimension d. 2. ... we choose the constant \alpha_max _E = 1, see also the discussion in Guermond et al. (2011).
However, it seems that Jon has found that in his computations
3. "For the temperature-dependent models in this paper, the values chosen for the stabilization parameters are the default values for ASPECT, \alpha_max = 0.078, and \alpha_E = 0.33."
I have asked Jon to double check that this is what is in the parameter file that is output with the values of the parameters that have been used in a particular computation.
Nevertheless, I thought it would be a good idea to ask on aspect-devel what current defaults are.
One other observation. I noticed that
if the dimension d = 3, then we have,
\alpha_max = 0.078 = 0.026 * 3 = = 0.026 * d
and then the statement in 1. concerning how \alpha_max is chosen is
consistent with the statement in 3., /except that our d should be /d =2.
Also is there a simple way to address this request from the reviewer?
“A comment on how they select the stabilization parameters values
are also needed for completeness.”
Comments, thoughts, explanations … ?
Thanks for your attention to this issue. I’m trying to ensure that what we write in a refereed journal article about ASPECT is correct, at least at the time at which we wrote it.
Happy New Year!