1. Problems on cluster computers

2. Thermochemistry questions

2.1. When preparing a thermally perfect gas model for use, I get a warning about missing CEA coefficients for viscosity and thermal conductivity for some species. Should I be worried? Why does this happen?

When preparing a thermally perfect gas model, Eilmer defaults to attempting to use the CEA coefficients for thermodynamics and transport properties. The thermodynamic coefficients have been taken from the CEA file thermo.inp, and the transport property coefficients are from trans.inp. If you look in trans.inp, you’ll notice that is has data for far fewer species than those listed in thermo.inp. In other words, the transport property data was not available or not important for the builders of CEA. So this answers the question why does this happen. It happens because the data is simply not available from CEA. What the prep-gas program will do is supply default values from the defaults.lua file. You can inspect that to see what the defaults are. They are most likely the properties for air.

The other question, "should I be worried?", has a more complex answer. It depends. If you are doing an inviscid simulation, then there’s nothing to be concerned about. This warning is related to transport properties. These only come into play for viscous simulations. If you are doing a viscous simulation, then you need to apply some judgement. Are these species with missing transport data minor species in the mixture? If so, their contribution to the bulk viscosity and thermal conductivity is probably minor. If this is the case, it would probably be quite acceptable to use the substituted air properties for these minor species.

But no, these missing species are really important to me?

Sounds like you’re doing a combustion problem. Usually these missing species properties arise for intermediate species in combustion processes. In that case, you’ll probably want to dip into the Grimech database instead. It is often more complete for these species. That is also available in Eilmer for many (but not all) species. You can configure this option in your input file for prep-gas. Add the following line to your input file::

options = {database='prefer-grimech'}

My species are still missing when I use the Grimech database!!!

Well, now it sounds like you’ll need to hunt down the data for the transport properties yourself. You can add them to your prepared gas model input file, or better yet, add them to the source code and send us your contribution. There is information on adding complete species and species data in: dgd/src/gas/species-database/README.rst.

3. Generic WTF?

3.1. What are time stamps?

as asked by Katrina (2017-04-26) and the Singapore group.

3.2. What is WC, WCtFT and WCtMS?

Wall Clock, Wall Clock till Final Time and Wall Clock till Maximum allowed Steps estimated in seconds.