Nonsmooth DAEs with Applications in Modeling Phase Changes

TitleNonsmooth DAEs with Applications in Modeling Phase Changes
Publication TypeBook Chapter
Year of Publication2019
AuthorsStechlinski P, Patrascu M, Barton PI
Book TitleApplications of Differential-Algebraic Equations: Examples and Benchmarks

A variety of engineering problems involve dynamic simulation and optimization, but exhibit a mixture of continuous and discrete behavior. Such hybrid continuous/discrete behavior can cause failure in traditional methods; theoretical and numerical treatments designed for smooth models may break down. Recently it has been observed that, for a number of operational problems, such hybrid continuous/discrete behavior can be accurately modeled using a nonsmooth differential-algebraic equations (DAEs) framework, now possessing a foundational well-posedness theory and a computationally relevant sensitivity theory. Numerical implementations that scale efficiently for large-scale problems are possible for nonsmooth DAEs. Moreover, this modeling approach avoids undesirable properties typical in other frameworks (e.g., hybrid automata); in this modeling paradigm, extraneous (unphysical) variables are often avoided, unphysical behaviors (e.g., Zeno phenomena) from modeling abstractions are not prevalent, and a priori knowledge of the evolution of the physical system (e.g., phase changes experienced in a flash process execution) is not needed. To illustrate this nonsmooth modeling paradigm, thermodynamic phase changes in a simple, but widely applicable flash process are modeled using nonsmooth DAEs.