Simple MACAW EOS

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Added (new features/APIs/variables/...)
 - [[PR556]](https://github.com/lanl/singularity-eos/pull/556) Add introspection into types available in the variant
+- [[PR560]](https://github.com/lanl/singularity-eos/pull/560) Add Simple MACAW EOS
 - [[PR564]](https://github.com/lanl/singularity-eos/pull/564) Removed Get() function from IndexableTypes since it could have unexpected consequences when a type wasn't present
 
 ### Fixed (Repair bugs, etc)

doc/sphinx/src/models.rst

@@ -21,6 +21,9 @@
 
 .. _PowerMG: https://www.osti.gov/biblio/1762624
 
+.. _SimpleMACAW: https://www.osti.gov/biblio/2479474
+
+.. _MACAW EOS: https://pubs.aip.org/aip/jap/article/134/12/125102/2912256
 
 EOS Models
 ===========
@@ -1320,6 +1323,56 @@ This constructor also optionally accepts `MeanAtomicProperties` for
 the atomic mass and number as a final optional parameter.
 
 
+Simple MACAW
+````````````
+The `Simple MACAW EOS <_SimpleMACAW>`_ is a simplified version of the `MACAW EOS <MACAW EOS>`_
+and is thermodynamically consistent.  It is constructed from a the Helmholtz
+free energy using a Murnaghan cold curve and a simplified thermal component
+from the MACAW EOS.
+
+Fundamentally, the equation of state can be written in Mie-Gruneisen form (with constant Gruneisen parameter) as:
+
+.. math::
+
+    P(v, e) = P_{\text{cold}}(v) + \Gamma_c \rho (e - e_{\text{cold}}(v))
+
+where the cold curves are given by:
+
+.. math::
+
+    e_{\text{cold}}(v) = A v_0 \Big[ \Big( \frac{v}{v_0} \Big)^{-B} + \Big( \frac{v}{v_0} \Big) B - (B+1) \Big]
+
+and 
+
+.. math::
+
+    p_{\text{cold}}(v) := -e'_{\text{cold}}(v) = AB \Big( \Big( \frac{v}{v_0} \Big)^{-(B+1)} - 1 \Big)
+
+The specific heat capacity at constant volume for this model is given by,
+
+.. math::
+
+    C_v(v, \tau) = C^\infty_v \frac{\tau^2 + 2\tau}{(\tau + 1)^2} \quad \text{where } \tau = \frac{T}{\theta(v)} \quad \text{ and } \quad \theta(v) := T_0 \Big( \frac{v}{v_c} \Big)^{-\Gamma_c}
+
+Note it obeys the expected physical behavior; that, :math:`\lim_{T\to 0^+} C_v(v,\tau(v,T)) = 0` and
+:math:`\lim_{T\to\infty} C_v(v,\tau(v,T) = C^\infty_v < \infty` (Dulong-Petit law).
+
+The constructor for the Simple MACAW EOS is
+
+.. code-block:: cpp
+
+  SimpleMACAW(const Real A, const Real B, const Real Cvinf, const Real v0,
+              const Real T0, const Real Gc)
+
+where ``A`` is :math:`A`, ``B`` is :math:`B`, ``Cvinf`` is :math:`C^\infty_v`,
+``v0`` is :math:`v_0`, ``T0`` is :math:`T_0`, ``Gc`` is :math:`\Gamma_c`.
+
+In order to maintain thermodynamic stability, a sufficient set of constraints
+is given by :math:`A > 0`, :math:`B > 0`, :math:`C^\infty_v > 0`, :math:`v_0 >
+0`, :math:`T_0 > 0`, and :math:`\Gamma_c \in (0,1]`. One can still select
+:math:`\Gamma_c > 1`, just note that the isothermal bulk modulus can be
+negative (the isentropic bulk modulus will still be positive though).
+
 JWL EOS
 ``````````
 

singularity-eos/CMakeLists.txt

@@ -53,6 +53,7 @@ register_headers(
     eos/eos_gruneisen.hpp
     eos/eos_vinet.hpp
     eos/eos_builder.hpp
+    eos/eos_simple_macaw.hpp
     eos/eos_jwl.hpp
     eos/eos_helmholtz.hpp
     eos/eos_sap_polynomial.hpp

singularity-eos/eos/eos_models.hpp

@@ -1,5 +1,5 @@
 //------------------------------------------------------------------------------
-// © 2021-2024. Triad National Security, LLC. All rights reserved.  This
+// © 2021-2025. Triad National Security, LLC. All rights reserved.  This
 // program was produced under U.S. Government contract 89233218CNA000001
 // for Los Alamos National Laboratory (LANL), which is operated by Triad
 // National Security, LLC for the U.S.  Department of Energy/National
@@ -28,6 +28,7 @@
 #include <singularity-eos/eos/eos_noble_abel.hpp>
 #include <singularity-eos/eos/eos_powermg.hpp>
 #include <singularity-eos/eos/eos_sap_polynomial.hpp>
+#include <singularity-eos/eos/eos_simple_macaw.hpp>
 #include <singularity-eos/eos/eos_spiner.hpp>
 #include <singularity-eos/eos/eos_stellar_collapse.hpp>
 #include <singularity-eos/eos/eos_stiff.hpp>