Notes on
The goal of
Constant Composition
Consider an isentropically stratified atmosphere, with a constant
composition as a function of
and the definition of
So, at constant entropy, from the definition of
Comparing to the definition of
Therefore,
This means that if we have a constant composition and an isentropically stratified atmosphere, as we displace a fluid element, it will always remain neutrally buoyant.
Composition Gradient
If there is a change in composition with
On the Effect of Chemical Potential
In MAESTRO, we do things in an operator split fashion — the hydro is
de-coupled from the burning. This means that during the hydro parts
of the algorithm (where
Derivation of
In paper I,
where
where the subscript
used CG’s discussion of the various adiabatic
Even in the presence of reactions, Eq.365 can be rewritten as was done in paper I:
where
Following the results of paper I, we want to find a relation
between
For an equation of state
We define another logarithmic derivative
and therefore
From here we get the general statement
which must hold for an adiabatic process as well, and therefore we have
where we use CG’s definition of
where the subscript AD means along an adiabat. We now derive an expression
for
The first law of thermodynamics can be written as
where
where we have used
and
Now we need to evaluate
exactly the same result if we were to exclude species information. Similarly, we can find an expression for the derivative of energy with respect to composition
Plugging these back into Eq.379 we have
or
We can obtain an expression for the specific heat at constant pressure from the enthalpy
The first term on the rhs can be obtained from writing
and
Dividing this by Eq.383 and using the relation between the
Plugging [eq:pchirho] into Eq.368 and rewriting the
partial derivative of
Recalling Derivation of
Recall from paper I that
in such a fashion that we ended up with an equation of the form
The derivation in Appendix B of paper I for a