KAPPA: Kinetic approach to physical processes in atmospheres library in C++
KAPPA, an open-source software library for the computation of thermodynamic and transport properties in non-equilibrium gas flows and species production rates, is presented. Thermodynamic properties rely on custom databases which describe the characteristics of atoms and molecules and interaction features. Mixture thermodynamic properties are formulated from species quantities. Species production rates are based on elementary chemical reactions and vibrational energy transitions. Transport properties are derived from kinetic theory which provides relationships for transport coefficients depending on the flow model. Several levels of non-equilibrium flow description are implemented: the detailed state-to-state (STS) approach, multi-temperature and one-temperature models. Sets of transport coefficients depend on the deviation from equilibrium; in the state-to-state model, they include state-resolved diffusion coefficients for each pair of vibrational states. A highly modular, object-oriented application program interface (API) has been developed. The adopted object-oriented programming paradigm (OOP), along with the implemented models of state-resolved physico-chemical relaxation rates, is presented. The design of the library allows it to be easily included in existing CFD codes and is aimed at code reusability and readability.